Will question

[Fireinthegrate]

M mum was taken ill a few months ago. She now needs care. Dad's Will leaves everything to her and vice versa.
However, if Dad dies first and everthing goes to Mum, the money will get swallowed up eventually by care costa for Mum.
Can Dad change his Will and leave everything to me and my siblings instead of to Mum?
Is this allowed?

Who is going to be paying for your mum's care at the moment and who do you expect to pay for it in the future. Are you asking if he can deliberately change his Will so that your mum doesn't have to pay for her care and you benefit instead,

Their money has been separated out and she pays for her own care. (Advised to do this by solicitor, accountant and social care)

Yes he can
Relatively common thing to do

He can do what he wants with his half of the money. Perfectly normal and legal!

Sounds good, if she is paying for her own care. Will mum have to alter her Will too so she doesn't pay for his care if it's needed.