In the US , the kind of thing you appear to be talking about is a fiduciary they have control of your money , but also have a legal obligation to use that money in your best interests . My exwife is was ? , I don ' t talk to her at all anymore was her mom ' s fiduciary , because her mother is bipolar , has PTSD , and is unable to take care of herself . If my exwife spent even a penny of her mom ' s money for herself , she would be violating her legal fiduciary duty . I don ' t know if this is the case for you . I don ' t know if that relationship has to be made formal , or if you can argue that it was an informal relationship , but that you had an expectation that she would use your money for your benefit . You definitely need an attorney for this , and you need to be prepared to have your whole family think that you ' re a terrible person for suing your grandmother . You should sue her , if your attorney says you have a decent legal case , and you aren ' t a terrible person for doing so . nbspYou have an SO boyfriend ? , fiancee ? that tells me that someone must like your personality .