Apologies for this relating to benefits not usually discussed here but I'm hoping someone might know the answer to this.
A and B are married. A takes care of all the finances and accounts are in his name. A applies for and gets Council Tax reduction and Housing Benefit for some years. Two years ago A dies.
B's children now find that A and B's joint capital exceeded the 16K limit for a period during which they were getting Council Tax reduction and Housing Benefit before the tenancy and the Council Tax were put in her name. B suffers from Dementia and has no knowledge of all this
I don't think anybody online can give you a definitive answer as you need someone to look at the A's estate, however you mention shared assets which would imply liability.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems