Legal Question in Civil Rights Law in Illinois

If the paperwork sent to the insurance company to release the check was "correct" but either a fraud or a forgery, your rights, if any, may be against the family members who manufactured the paperwork, unless the insurance company should have known better, in which case the insurance company may have some responsibility. This is not civil rights law; it is insurance law, and possibly probate: normally insurance doesn't go through probate unless the insurance was payable to the estate, in which case the administrator and/or executor or your grandmother's estate would be involved. It may also be tax fraud because there can be taxes due on insurance proceeds. See your OWN attorney to get things started. Otherwise this is too complicated and without seeing all the paperwork no reliable legal advice can be given.