The tax threshold and couples

MorganFire

This might seem like a stupid question so sorry in advance. 
The PAYE tax threshold. Let's say it's £12k for argument's sake. 
If you're living as a couple (or even married) and you both have a full time job, each wage is protected for the first £12k right? 
But if you are the sole income earner for a couple with children, does this change? I know there's marriage allowance but that's like £1k.
Is the income threshold based on "household" income? Or "individual" income? 

Any information welcome. I'm just struggling to find out how it works and all Google wants to talk about is the marriage tax allowance.

Dazed_and_C0nfused

Household income isn't a thing for tax purposes.

Assuming neither of you were born in 1935 or earlier then the only option available to you (assuming neither is a higher rate payer and you are married or in a civil partnership) is Marriage Allowance.

Marriage Allowance is where the applicant agrees to a reduced Personal Allowance (£11,310 instead of £12,570) and the recipient gets £252 knocked off their tax liability.