Evicting a family member

FlorayG

All this argument over tenant or lodger I think comes down to one thing - does Fluffy still have her own bedroom in the flat? An inhabitant can't be assumed to have a legal tenancy if the landlord has retained sole use of a room, surely?.

ThisIsWeird

_Penny_Dreadful said:

Are you saying the legislation is definitive? :-)

You are undoubtedly better informed than me, but if you are citing the above legislation, then may I ask;

1) At what point did Fluffy's sis's status as a 'lodger' change? How many weeks of Fluffy's absence triggered this?

2) What should Fluffy, as a lay person who'd kindly allowed her sis' to occupy a spare bedroom for a trivial rent, have done - and should have known to have done - under these circumstances, to prevent any such issues? Ie, so that her sis remained a 'lodger'?

3) If the sis gained automatic 'rights' through Fluffy's absence, how long will it similarly take on Fluffy's return for sis 'lodger' status to be revoked?

4) If Fluffy moves back in, and shares the house with sis under the previous conditions, what can sis do?

Are you being deliberately obtuse or do you genuinely not understand? 

The legislation defines what is a resident landlord. The OP does not fit the criteria. 

1. When the OP no longer met the criteria of a resident landlord the sister ceased to be an excluded occupier. 
2. Ignorance is not a defence. If it were then all those landlords who end up issuing invalid section 21 notices due to a missing piece of PI would still be granted a possession order. “It wasn’t my fault m’lud. I’m an accidental landlord, I didn’t know I was supposed to give the tenant a how-to-rent booklet.” What the OP should have done was either evict the sister before the OP moved out or issued the sister with a written AST. There’s a reason many of the seasoned landlords on the forum say the number one rule is never let to friends or family. This is a prime example of why it’s a bad idea. People think because it’s a friend or family member they can be lackadaisical with the paper work…you can’t be because when it goes wrong it goes very badly wrong and relationships are ruined. 
3. What makes you think the OP can just move back in. A couple of my BTL are former residences do you think I can move back in and make the occupants lodgers? Even with a HMO when the landlord lets out the rooms on an individual basis and then a tenant moves out making a room available the landlord taking up occupation in the room doesn’t make the tenants renting the other rooms excluded occupiers. 
4. It depends on how belligerent the sister is feeling. The best outcome for the OP would be the sister rolling over and accepting the situation. The worst is the sister getting and acting upon advice from the local authority or tenant organisation informing her of her rights and the OP being removed from the property. The OP could end up like Louis Scudder from Kent. 

No, I'm really not trying to be either. Honestly.

1) When did the OP no longer meet this criterion? When? At what point? Date? You say it's definitive. I see nothing that's definitive in that legislation.

2) Ignorance is no defence, that's generally true. But intent could be. All these other examples you cite are all about LL's who have intent - they chose to be a LL and to have tenants. If they then make an error - deliberately or accidentally - they are punished (often quite punitively). Fluffy is not an accidental landlord - she's a flat owner who allowed her sis to lodge with her.

3) Fluffy can move in because nothing has actually changed. Her sis has not made any claim to the contrary - she's just ignoring Fluffy. Not exactly acting in a 'tenant-like behaviour' should it come to this...

4) Yes, that's the worst case. So I'm suggesting a method to pre-empt that. If the sis becomes bolshie, then she'll become bolshie. But if she does so before Fluffy even gets a foot in the door, Fluffy will be in a worse situation.

Even if this became 'legal', this is not the same as an actual LL who is either lax or is deliberately bending the rules.

Could you put a timescale on point 1, for example?

What would you suggest Fluffy does?

And why do they call you 'Penny'?

_Penny_Dreadful

ThisIsWeird said:

_Penny_Dreadful said:

Are you saying the legislation is definitive? :-)

You are undoubtedly better informed than me, but if you are citing the above legislation, then may I ask;

1) At what point did Fluffy's sis's status as a 'lodger' change? How many weeks of Fluffy's absence triggered this?

2) What should Fluffy, as a lay person who'd kindly allowed her sis' to occupy a spare bedroom for a trivial rent, have done - and should have known to have done - under these circumstances, to prevent any such issues? Ie, so that her sis remained a 'lodger'?

3) If the sis gained automatic 'rights' through Fluffy's absence, how long will it similarly take on Fluffy's return for sis 'lodger' status to be revoked?

4) If Fluffy moves back in, and shares the house with sis under the previous conditions, what can sis do?

Are you being deliberately obtuse or do you genuinely not understand? 

The legislation defines what is a resident landlord. The OP does not fit the criteria. 

1. When the OP no longer met the criteria of a resident landlord the sister ceased to be an excluded occupier. 
2. Ignorance is not a defence. If it were then all those landlords who end up issuing invalid section 21 notices due to a missing piece of PI would still be granted a possession order. “It wasn’t my fault m’lud. I’m an accidental landlord, I didn’t know I was supposed to give the tenant a how-to-rent booklet.” What the OP should have done was either evict the sister before the OP moved out or issued the sister with a written AST. There’s a reason many of the seasoned landlords on the forum say the number one rule is never let to friends or family. This is a prime example of why it’s a bad idea. People think because it’s a friend or family member they can be lackadaisical with the paper work…you can’t be because when it goes wrong it goes very badly wrong and relationships are ruined. 
3. What makes you think the OP can just move back in. A couple of my BTL are former residences do you think I can move back in and make the occupants lodgers? Even with a HMO when the landlord lets out the rooms on an individual basis and then a tenant moves out making a room available the landlord taking up occupation in the room doesn’t make the tenants renting the other rooms excluded occupiers. 
4. It depends on how belligerent the sister is feeling. The best outcome for the OP would be the sister rolling over and accepting the situation. The worst is the sister getting and acting upon advice from the local authority or tenant organisation informing her of her rights and the OP being removed from the property. The OP could end up like Louis Scudder from Kent. 

No, I'm really not trying to be either. Honestly.

1) When did the OP no longer meet this criterion? When? At what point? Date? You say it's definitive. I see nothing that's definitive in that legislation.

2) Ignorance is no defence, that's generally true. But intent could be. All these other examples you cite are all about LL's who have intent - they chose to be a LL and to have tenants. If they then make an error - deliberately or accidentally - they are punished (often quite punitively). Fluffy is not an accidental landlord - she's a flat owner who allowed her sis to lodge with her.

3) Fluffy can move in because nothing has actually changed. Her sis has not made any claim to the contrary - she's just ignoring Fluffy. Not exactly acting in a 'tenant-like behaviour' should it come to this...

4) Yes, that's the worst case. So I'm suggesting a method to pre-empt that. If the sis becomes bolshie, then she'll become bolshie. But if she does so before Fluffy even gets a foot in the door, Fluffy will be in a worse situation.

Even if this became 'legal', this is not the same as an actual LL who is either lax or is deliberately bending the rules.

Could you put a timescale on point 1, for example?

What would you suggest Fluffy does?

And why do they call you 'Penny'?

1. I have already answered this question. 
2. The OP deliberately became a landlord the second the sister moved in and started paying rent. The legislation clearly defines a resident landlord so the intent is irrelevant. It’s the facts of the matter that are important and factually the OP has not occupied that property as their only or main home for 4+ years. 
3. Legally quite a bit has changed as several posters have pointed out. 
4. It is the same as any other landlord. The legislation is not different when the landlord happens to share DNA with the tenant. 

What I would do is arrange to meet the sister for a coffee somewhere neutral to sound her out. Perhaps floating the idea of me moving back in to see how she reacts. If that doesn’t go the way I hoped then I’d try mediation or revisit the idea of her buying me out. If that fails take the nuclear option which I have already described in this thread. I’d also see about getting off the council tax and close the utility accounts. It’s all a huge mess and the last thing the OP needs at this time. 

silvercar

No good deed goes unpunished.

_Penny_Dreadful said:

ThisIsWeird said:

_Penny_Dreadful said:

Are you saying the legislation is definitive? :-)

You are undoubtedly better informed than me, but if you are citing the above legislation, then may I ask;

1) At what point did Fluffy's sis's status as a 'lodger' change? How many weeks of Fluffy's absence triggered this?

2) What should Fluffy, as a lay person who'd kindly allowed her sis' to occupy a spare bedroom for a trivial rent, have done - and should have known to have done - under these circumstances, to prevent any such issues? Ie, so that her sis remained a 'lodger'?

3) If the sis gained automatic 'rights' through Fluffy's absence, how long will it similarly take on Fluffy's return for sis 'lodger' status to be revoked?

4) If Fluffy moves back in, and shares the house with sis under the previous conditions, what can sis do?

Are you being deliberately obtuse or do you genuinely not understand? 

The legislation defines what is a resident landlord. The OP does not fit the criteria. 

1. When the OP no longer met the criteria of a resident landlord the sister ceased to be an excluded occupier. 
2. Ignorance is not a defence. If it were then all those landlords who end up issuing invalid section 21 notices due to a missing piece of PI would still be granted a possession order. “It wasn’t my fault m’lud. I’m an accidental landlord, I didn’t know I was supposed to give the tenant a how-to-rent booklet.” What the OP should have done was either evict the sister before the OP moved out or issued the sister with a written AST. There’s a reason many of the seasoned landlords on the forum say the number one rule is never let to friends or family. This is a prime example of why it’s a bad idea. People think because it’s a friend or family member they can be lackadaisical with the paper work…you can’t be because when it goes wrong it goes very badly wrong and relationships are ruined. 
3. What makes you think the OP can just move back in. A couple of my BTL are former residences do you think I can move back in and make the occupants lodgers? Even with a HMO when the landlord lets out the rooms on an individual basis and then a tenant moves out making a room available the landlord taking up occupation in the room doesn’t make the tenants renting the other rooms excluded occupiers. 
4. It depends on how belligerent the sister is feeling. The best outcome for the OP would be the sister rolling over and accepting the situation. The worst is the sister getting and acting upon advice from the local authority or tenant organisation informing her of her rights and the OP being removed from the property. The OP could end up like Louis Scudder from Kent. 

No, I'm really not trying to be either. Honestly.

1) When did the OP no longer meet this criterion? When? At what point? Date? You say it's definitive. I see nothing that's definitive in that legislation.

2) Ignorance is no defence, that's generally true. But intent could be. All these other examples you cite are all about LL's who have intent - they chose to be a LL and to have tenants. If they then make an error - deliberately or accidentally - they are punished (often quite punitively). Fluffy is not an accidental landlord - she's a flat owner who allowed her sis to lodge with her.

3) Fluffy can move in because nothing has actually changed. Her sis has not made any claim to the contrary - she's just ignoring Fluffy. Not exactly acting in a 'tenant-like behaviour' should it come to this...

4) Yes, that's the worst case. So I'm suggesting a method to pre-empt that. If the sis becomes bolshie, then she'll become bolshie. But if she does so before Fluffy even gets a foot in the door, Fluffy will be in a worse situation.

Even if this became 'legal', this is not the same as an actual LL who is either lax or is deliberately bending the rules.

Could you put a timescale on point 1, for example?

What would you suggest Fluffy does?

And why do they call you 'Penny'?

1. I have already answered this question. 
2. The OP deliberately became a landlord the second the sister moved in and started paying rent. The legislation clearly defines a resident landlord so the intent is irrelevant. It’s the facts of the matter that are important and factually the OP has not occupied that property as their only or main home for 4+ years. 
3. Legally quite a bit has changed as several posters have pointed out. 
4. It is the same as any other landlord. The legislation is not different when the landlord happens to share DNA with the tenant. 

What I would do is arrange to meet the sister for a coffee somewhere neutral to sound her out. Perhaps floating the idea of me moving back in to see how she reacts. If that doesn’t go the way I hoped then I’d try mediation or revisit the idea of her buying me out. If that fails take the nuclear option which I have already described in this thread. I’d also see about getting off the council tax and close the utility accounts. It’s all a huge mess and the last thing the OP needs at this time. 

Becoming a landlord to a lodger to help out a family member is clearly very different to becoming a landlord of an unrelated tenant. If any of this got to court, a judge could well appreciate the difference. 

"I'm temporarily moving to look after my relatives" is very different from "I'm moving out and giving you the tenancy of the whole property." 

ThisIsWeird

silvercar said:

No good deed goes unpunished.

_Penny_Dreadful said:

ThisIsWeird said:

_Penny_Dreadful said:

Are you saying the legislation is definitive? :-)

You are undoubtedly better informed than me, but if you are citing the above legislation, then may I ask;

1) At what point did Fluffy's sis's status as a 'lodger' change? How many weeks of Fluffy's absence triggered this?

2) What should Fluffy, as a lay person who'd kindly allowed her sis' to occupy a spare bedroom for a trivial rent, have done - and should have known to have done - under these circumstances, to prevent any such issues? Ie, so that her sis remained a 'lodger'?

3) If the sis gained automatic 'rights' through Fluffy's absence, how long will it similarly take on Fluffy's return for sis 'lodger' status to be revoked?

4) If Fluffy moves back in, and shares the house with sis under the previous conditions, what can sis do?

Are you being deliberately obtuse or do you genuinely not understand? 

The legislation defines what is a resident landlord. The OP does not fit the criteria. 

1. When the OP no longer met the criteria of a resident landlord the sister ceased to be an excluded occupier. 
2. Ignorance is not a defence. If it were then all those landlords who end up issuing invalid section 21 notices due to a missing piece of PI would still be granted a possession order. “It wasn’t my fault m’lud. I’m an accidental landlord, I didn’t know I was supposed to give the tenant a how-to-rent booklet.” What the OP should have done was either evict the sister before the OP moved out or issued the sister with a written AST. There’s a reason many of the seasoned landlords on the forum say the number one rule is never let to friends or family. This is a prime example of why it’s a bad idea. People think because it’s a friend or family member they can be lackadaisical with the paper work…you can’t be because when it goes wrong it goes very badly wrong and relationships are ruined. 
3. What makes you think the OP can just move back in. A couple of my BTL are former residences do you think I can move back in and make the occupants lodgers? Even with a HMO when the landlord lets out the rooms on an individual basis and then a tenant moves out making a room available the landlord taking up occupation in the room doesn’t make the tenants renting the other rooms excluded occupiers. 
4. It depends on how belligerent the sister is feeling. The best outcome for the OP would be the sister rolling over and accepting the situation. The worst is the sister getting and acting upon advice from the local authority or tenant organisation informing her of her rights and the OP being removed from the property. The OP could end up like Louis Scudder from Kent. 

No, I'm really not trying to be either. Honestly.

1) When did the OP no longer meet this criterion? When? At what point? Date? You say it's definitive. I see nothing that's definitive in that legislation.

2) Ignorance is no defence, that's generally true. But intent could be. All these other examples you cite are all about LL's who have intent - they chose to be a LL and to have tenants. If they then make an error - deliberately or accidentally - they are punished (often quite punitively). Fluffy is not an accidental landlord - she's a flat owner who allowed her sis to lodge with her.

3) Fluffy can move in because nothing has actually changed. Her sis has not made any claim to the contrary - she's just ignoring Fluffy. Not exactly acting in a 'tenant-like behaviour' should it come to this...

4) Yes, that's the worst case. So I'm suggesting a method to pre-empt that. If the sis becomes bolshie, then she'll become bolshie. But if she does so before Fluffy even gets a foot in the door, Fluffy will be in a worse situation.

Even if this became 'legal', this is not the same as an actual LL who is either lax or is deliberately bending the rules.

Could you put a timescale on point 1, for example?

What would you suggest Fluffy does?

And why do they call you 'Penny'?

1. I have already answered this question. 
2. The OP deliberately became a landlord the second the sister moved in and started paying rent. The legislation clearly defines a resident landlord so the intent is irrelevant. It’s the facts of the matter that are important and factually the OP has not occupied that property as their only or main home for 4+ years. 
3. Legally quite a bit has changed as several posters have pointed out. 
4. It is the same as any other landlord. The legislation is not different when the landlord happens to share DNA with the tenant. 

What I would do is arrange to meet the sister for a coffee somewhere neutral to sound her out. Perhaps floating the idea of me moving back in to see how she reacts. If that doesn’t go the way I hoped then I’d try mediation or revisit the idea of her buying me out. If that fails take the nuclear option which I have already described in this thread. I’d also see about getting off the council tax and close the utility accounts. It’s all a huge mess and the last thing the OP needs at this time. 

Becoming a landlord to a lodger to help out a family member is clearly very different to becoming a landlord of an unrelated tenant. If any of this got to court, a judge could well appreciate the difference. 

"I'm temporarily moving to look after my relatives" is very different from "I'm moving out and giving you the tenancy of the whole property." 

Absolutely. Of course it's bludy different.

ThisIsWeird

_Penny_Dreadful said:

ThisIsWeird said:

_Penny_Dreadful said:

Are you saying the legislation is definitive? :-)

You are undoubtedly better informed than me, but if you are citing the above legislation, then may I ask;

1) At what point did Fluffy's sis's status as a 'lodger' change? How many weeks of Fluffy's absence triggered this?

2) What should Fluffy, as a lay person who'd kindly allowed her sis' to occupy a spare bedroom for a trivial rent, have done - and should have known to have done - under these circumstances, to prevent any such issues? Ie, so that her sis remained a 'lodger'?

3) If the sis gained automatic 'rights' through Fluffy's absence, how long will it similarly take on Fluffy's return for sis 'lodger' status to be revoked?

4) If Fluffy moves back in, and shares the house with sis under the previous conditions, what can sis do?

Are you being deliberately obtuse or do you genuinely not understand? 

The legislation defines what is a resident landlord. The OP does not fit the criteria. 

1. When the OP no longer met the criteria of a resident landlord the sister ceased to be an excluded occupier. 
2. Ignorance is not a defence. If it were then all those landlords who end up issuing invalid section 21 notices due to a missing piece of PI would still be granted a possession order. “It wasn’t my fault m’lud. I’m an accidental landlord, I didn’t know I was supposed to give the tenant a how-to-rent booklet.” What the OP should have done was either evict the sister before the OP moved out or issued the sister with a written AST. There’s a reason many of the seasoned landlords on the forum say the number one rule is never let to friends or family. This is a prime example of why it’s a bad idea. People think because it’s a friend or family member they can be lackadaisical with the paper work…you can’t be because when it goes wrong it goes very badly wrong and relationships are ruined. 
3. What makes you think the OP can just move back in. A couple of my BTL are former residences do you think I can move back in and make the occupants lodgers? Even with a HMO when the landlord lets out the rooms on an individual basis and then a tenant moves out making a room available the landlord taking up occupation in the room doesn’t make the tenants renting the other rooms excluded occupiers. 
4. It depends on how belligerent the sister is feeling. The best outcome for the OP would be the sister rolling over and accepting the situation. The worst is the sister getting and acting upon advice from the local authority or tenant organisation informing her of her rights and the OP being removed from the property. The OP could end up like Louis Scudder from Kent. 

No, I'm really not trying to be either. Honestly.

1) When did the OP no longer meet this criterion? When? At what point? Date? You say it's definitive. I see nothing that's definitive in that legislation.

2) Ignorance is no defence, that's generally true. But intent could be. All these other examples you cite are all about LL's who have intent - they chose to be a LL and to have tenants. If they then make an error - deliberately or accidentally - they are punished (often quite punitively). Fluffy is not an accidental landlord - she's a flat owner who allowed her sis to lodge with her.

3) Fluffy can move in because nothing has actually changed. Her sis has not made any claim to the contrary - she's just ignoring Fluffy. Not exactly acting in a 'tenant-like behaviour' should it come to this...

4) Yes, that's the worst case. So I'm suggesting a method to pre-empt that. If the sis becomes bolshie, then she'll become bolshie. But if she does so before Fluffy even gets a foot in the door, Fluffy will be in a worse situation.

Even if this became 'legal', this is not the same as an actual LL who is either lax or is deliberately bending the rules.

Could you put a timescale on point 1, for example?

What would you suggest Fluffy does?

And why do they call you 'Penny'?

1. I have already answered this question. 
2. The OP deliberately became a landlord the second the sister moved in and started paying rent. The legislation clearly defines a resident landlord so the intent is irrelevant. It’s the facts of the matter that are important and factually the OP has not occupied that property as their only or main home for 4+ years. 
3. Legally quite a bit has changed as several posters have pointed out. 
4. It is the same as any other landlord. The legislation is not different when the landlord happens to share DNA with the tenant. 

What I would do is arrange to meet the sister for a coffee somewhere neutral to sound her out. Perhaps floating the idea of me moving back in to see how she reacts. If that doesn’t go the way I hoped then I’d try mediation or revisit the idea of her buying me out. If that fails take the nuclear option which I have already described in this thread. I’d also see about getting off the council tax and close the utility accounts. It’s all a huge mess and the last thing the OP needs at this time. 

1) No you haven't. 

mybestattempt

I feel must say I support the stance @_Penny_Dreadful takes on this situation.

So far as litigation is concerned the fact the landlord and tenant are blood relatives is not relevant if the landlord wants to evict.

A judge must establish the relevant facts and apply the legislation.

I'm my view the relevant facts are what date did the sister move in and what date did the OP move out.

I'm not even sure there was a period of when both lived in the property (the OP has just said 2020) but even if there was, the from date the OP moved out she was not a resident landlord.

Grumpy_chap

There is clearly a difference of opinion in the forum as to whether the Sister is a Tenant or a Lodger.
I think my take would veer towards the Sister being a Tenant.

It really does need the OP to take professional advice to establish the status of the Sister.

If the Sister is a Lodger, the OP can move back in and the Sister has very few rights.  If the Sister is, in fact, a Tenant and the OP moves back in, the OP may have acted unlawfully.

If the Sister is a Tenant, the OP needs to follow a clear process to evict the Sister.  Starting this process if the Sister is, in fact, a Lodger may be unwise as the process itself may be sufficient for the Sister to successfully argue the status of Tenant.  It is very rare, but this might be a genuine case of "accidental landlord" and I suspect the necessary steps to support a successful eviction (if the Sister is a Tenant) were never followed at the outset.

You would hope, really, that the OP could simply have a conversation with her Sister, explain she will need to move back and not remain in the rental property any longer, and the Sister will simply agree to move on.  The whole premise of the thread seems to be that the Sister is not acting in that honourable way.

ThisIsWeird

mybestattempt said:
A judge must establish the relevant facts and apply the legislation.

Judges apply the intention of the law or legislation.

When compulsory motorbike helmets were first introduced, one wag passed his arm through his full-face and wore it on his elbow. The law didn't actually state it had to be worn on the head, claimed the wisearris. The judge told him what the obvious intention of the law was, and he was fined (or perhaps just given a warning). I don't think that's an urban myth, but it could be...

If Fluffy seeks legal advice, and carries out the pedantic recommendation, the chances are very high that she'll find herself in an utter mess, possibly quite a costly one*, as a direct result. Once 'action' begins, the other party will likely seek advice. If this sis gains 'tenant' status as a result, that would clearly be an absurdity in this case.

My advice to Fluffy remains. Worst case, it doesn't work, and then she's back to square one - but living under her own roof if she wishes.

*'Tenant': secured deposit? Annual gas inspections? Electrical check on moving in? LL's insurance cover? Lawdie.

_Penny_Dreadful

ThisIsWeird said:

_Penny_Dreadful said:

ThisIsWeird said:

_Penny_Dreadful said:

Are you saying the legislation is definitive? :-)

You are undoubtedly better informed than me, but if you are citing the above legislation, then may I ask;

1) At what point did Fluffy's sis's status as a 'lodger' change? How many weeks of Fluffy's absence triggered this?

2) What should Fluffy, as a lay person who'd kindly allowed her sis' to occupy a spare bedroom for a trivial rent, have done - and should have known to have done - under these circumstances, to prevent any such issues? Ie, so that her sis remained a 'lodger'?

3) If the sis gained automatic 'rights' through Fluffy's absence, how long will it similarly take on Fluffy's return for sis 'lodger' status to be revoked?

4) If Fluffy moves back in, and shares the house with sis under the previous conditions, what can sis do?

Are you being deliberately obtuse or do you genuinely not understand? 

The legislation defines what is a resident landlord. The OP does not fit the criteria. 

1. When the OP no longer met the criteria of a resident landlord the sister ceased to be an excluded occupier. 
2. Ignorance is not a defence. If it were then all those landlords who end up issuing invalid section 21 notices due to a missing piece of PI would still be granted a possession order. “It wasn’t my fault m’lud. I’m an accidental landlord, I didn’t know I was supposed to give the tenant a how-to-rent booklet.” What the OP should have done was either evict the sister before the OP moved out or issued the sister with a written AST. There’s a reason many of the seasoned landlords on the forum say the number one rule is never let to friends or family. This is a prime example of why it’s a bad idea. People think because it’s a friend or family member they can be lackadaisical with the paper work…you can’t be because when it goes wrong it goes very badly wrong and relationships are ruined. 
3. What makes you think the OP can just move back in. A couple of my BTL are former residences do you think I can move back in and make the occupants lodgers? Even with a HMO when the landlord lets out the rooms on an individual basis and then a tenant moves out making a room available the landlord taking up occupation in the room doesn’t make the tenants renting the other rooms excluded occupiers. 
4. It depends on how belligerent the sister is feeling. The best outcome for the OP would be the sister rolling over and accepting the situation. The worst is the sister getting and acting upon advice from the local authority or tenant organisation informing her of her rights and the OP being removed from the property. The OP could end up like Louis Scudder from Kent. 

No, I'm really not trying to be either. Honestly.

1) When did the OP no longer meet this criterion? When? At what point? Date? You say it's definitive. I see nothing that's definitive in that legislation.

2) Ignorance is no defence, that's generally true. But intent could be. All these other examples you cite are all about LL's who have intent - they chose to be a LL and to have tenants. If they then make an error - deliberately or accidentally - they are punished (often quite punitively). Fluffy is not an accidental landlord - she's a flat owner who allowed her sis to lodge with her.

3) Fluffy can move in because nothing has actually changed. Her sis has not made any claim to the contrary - she's just ignoring Fluffy. Not exactly acting in a 'tenant-like behaviour' should it come to this...

4) Yes, that's the worst case. So I'm suggesting a method to pre-empt that. If the sis becomes bolshie, then she'll become bolshie. But if she does so before Fluffy even gets a foot in the door, Fluffy will be in a worse situation.

Even if this became 'legal', this is not the same as an actual LL who is either lax or is deliberately bending the rules.

Could you put a timescale on point 1, for example?

What would you suggest Fluffy does?

And why do they call you 'Penny'?

1. I have already answered this question. 
2. The OP deliberately became a landlord the second the sister moved in and started paying rent. The legislation clearly defines a resident landlord so the intent is irrelevant. It’s the facts of the matter that are important and factually the OP has not occupied that property as their only or main home for 4+ years. 
3. Legally quite a bit has changed as several posters have pointed out. 
4. It is the same as any other landlord. The legislation is not different when the landlord happens to share DNA with the tenant. 

What I would do is arrange to meet the sister for a coffee somewhere neutral to sound her out. Perhaps floating the idea of me moving back in to see how she reacts. If that doesn’t go the way I hoped then I’d try mediation or revisit the idea of her buying me out. If that fails take the nuclear option which I have already described in this thread. I’d also see about getting off the council tax and close the utility accounts. It’s all a huge mess and the last thing the OP needs at this time. 

1) No you haven't. 

I have. This appears to be a case of I can explain it to you but I cannot understand it for you.