First of all, the signing thing sounds like you got put together, by your mother. However, your mother might be liable if she had a vested interest and basically stole your right to sue away from you. Was your attorney involved and present or who put together the agreement they could be liable for putting you together. It all depends on who was representing you and in your state what is the legal age for a minor? How old were you when you signed , and why the need to sign, and give up your rights , if you were a minor anyway, what difference would that make anyway. You must have had some kind of rights and that is why you got talked into signing. Did the attorney explain anything to you about what you were signing and were you given a copy of the document and was the document filed with the courts in a timely matter and witnessed and notarized. If the proper steps were not followed the document would not be valid. You might have not really even signed anything but someone signed for you , without your knowledge. Sounds good to me. Goodluck!

Also, you may have not signed away all your rights, depending on who was listed on the document you signed. By the way, your mother hopefully got a good settlement in the matter. She deserves to be taken care of and remember that sometimes the laws require a release from the minor to settle a case. Whatever you do don't let this drive a wedge in the middle of your family. Your father would not want that and blood is blood family is family. Sorry to here about your loss. Also another thing did your father have a will? If he did what does it say about assets obtained and heired to his survivors?