How to check a fake will?

Dear all, My father passed away in October 2014 without a Will. Recently, my brother started forcing me to sign an NOC saying that I, Neha (one of the legal heirs of my father), do not want anything from my father's assets. When i refused he got very aggressive and stooped to the level of threatening me. He said that if i do not budge he can produce a fake Will! I also remember that once he send me some documents related to a pending law suit of my father, after my father's demise, to continue that law suit. Is it possible to produce a fake Will? Is there a way i can counter his claim of fake Will? Regards, Neha