My mother stole my sister''s and my inheritance from a trust fund my father''s father left us.

I want to find a way to see if she still has it and, if she still does, if we would be able to get the money back. We know that she had a private account in my grandfather''s (her father''s) name. I, however, do not want to put my parents into bankruptcy. My mother is an undiagnosed sociopath and alcoholic and has been living like a queen while my sick father and little brother live like paupers. The only thing my father cares about is that he does not lose his house which my mother, being in charge of the finances, seems to be on the path of doing. I want to find a way to sue my mother for what she has taken without affecting my brother and father...is this possible?