brother obtained signatures fraudently

Sir, My father had 3 residential houses which are registered in his name. He died in the year 2001. For the past 10-15 years our terms with father were not cordial because our brother/sister always filed our father’s ears against us in order to grab his property. After his death when we approached for our share in property, my brother who has political connection, money and muscle power, threatened myself and my other two sisters that he would not give any share in the property but threatened us execute registered gift deed in his favor, otherwise he would go to any extent to harm us. Fearing our safety, we executed the Gift Deed in his favour. In return he paid us very nominal amount. He even made us sign on the stamp papers stating that henceforth we will not have any right in father’s other property, which we came to know later that there is an agricultural land in a village registered in the name of our father. Can we now approach the court to challenge the gift deed in spite of the fact that he has obtained our signatures on stamp papers fraudulently 13 years ago to prevent us from filing partition suit in future. Kindly reply me on the above. Sarwath Khan Secunderabad