Deed of Variation

Land_Registry

If the property is registered in your late Father's sole name then his executor(s) can deal with the sale by relying on the probate already granted. From you original post it appears that you are the sole executor named in the probate.

If you wish to transfer the legal ownership into your sole name prior to selling you can - you already appreciate that forms AP1, AS1 and ID1 are required to do that. However as others mention you can sell a registered property based on the current registered information plus probate. Most buyers are happy to complete on that basis.

The estate, namely his will and his beneficiaries, are relevant to the proceeds of sale. Namely once sold the monies received are then dealt with by you as the executor as appropriate and as agreed by beneficiaries or in this case your sister's own beneficiaries/next of kin for example. In my experience this 'all works' if every affected/interested party agrees to what happens re the monies.

Your brother in law does not need letters of administration/probate for your deceased sister as she was not a legal owner of your late Father's property. She had a beneficial interest that you can deal with as explained.

There's no deed of variation needed re your late Father's will as nothing needs to be varied it seems from your posts. I assume the reference to 2 year rule is linked to any variation of the will but as mentioned it seems that's not needed so the 2 years rule is irrelevant.

If there are issues re the will and beneficial shares/interests please do seek legal advice. That is where the complexities arise but they don't generally directly impact on the registered information