You have several options, but really should consult with an attorney before pursuing them, and if you do pursue them, you should let a lawyer help you:1) You can sue your sister and her attorney if you believe they tricked you into signing papers giving away your rights. You would sue them for the money you believe you should have gotten. In the course of the lawsuit, you will have legal processes available (called "discovery"), such as written interrogatories or questions, document requests, and subpoenas, to get information from your sister and her lawyer. If you can prove in to court that they deceived you into signing a waiver, you may be able to void, or set aside, that waiver so you can get the benefits, and/or get other monetary compensation from them. (Note one thing that will be an uphill struggle from you: the law presumes that people read and understood what they signed, and you had an absolute right to refuse to sign any papers unless you had the chance to read them in full first. A court could conclude that since you could have refused to sign, if you chose to sign without readin, you are bound to what you signed.)2) You could file a ethics complaint against the law with the state bar association. This will not directly get you money, but may put pressure on the attorney and may also result in you getting information.3) Stealing by tricking someone is still stealing, so in theory you could file a police report ad look to press charges. But you could be sued by the ones you press charges against if they turn out to not be supported by facts, so you should definitely discuss this option with a lawyer before proceeding, to understand your potential exposure.