My Step sister borrowed a large sum of money from my step mum (her mother) and my dad which she and her DH used as a deposit for their property. The property as far as I know is in their joint names. There was no formal loan agreement put in place because it was "family" but she has (up until her mum died) been paying interest on the money. Anyway her mum died last year and now my dad wants the money paid back. Step sis won't even talk about it and says it was her mum's money so now it's hers. Obviously morally I think she should pay it back, but legally do you think my dad has a case given there's no written agreement? He doesn't want to waste more money on solicitors if he doesn't stand a chance.