How can i get my father share in his ancestral property.

Dear Sir, My grand father has 3 son;s among them my father is elder. Among three my father is only well educated and has been retired from Government Job. My grand father got the property from his mother-in-law and she divided enough property equally in all 3 grand son's. Now i describe my case below: Earlier we lived as a joint family in a posh colony in Delhi. When i was in class 3rd, my father got transfer in panipat in his job. When question arises for my father share both uncle ( included my Grand father maybe ) refuse to give. My grand father live with my uncle as grand parents has no understanding with my mother. My both uncle got married in same house. Both aunties are real sister, but my mother from different home. After few years my uncle told my father either he take his family with him or they will beat us. As there were no understanding between ladies. My father took us with him in a house provided in government employee colony. After few years we get back to our grandparents home ( to take our left material / furniture ), we find they had put another iron gate before our door. When we ask for the key they refuse to give. We have no such communication with them till now except me and my sister marriage in which only grandparents come. Hardly 2-3 times my grand parents visit us as my father took home in Delhi after his retirement in 2008. But they never talk about my father share. My father also visit his home in intervals and when my grand father or mother got ill. After leaving my grand parents home, my uncle sold my plots of my father by doing his fake signature as in earlier days maybe it was not mandatory for seller to present in court ( i don't know how they sell all such properties. ). My father never object, it seems very strange. Moreover my father also never talk with them about his share ( as he said all his plots was sold by both uncle by signature of my grand father) and if he put case my grandfather will be behind bars. Now my grand father is about 95 years old and on bed. I don't think that court will put him behind bars. I just want justice. kindly guide me how can i get my share in ancestral property if my father don't take any step against his brothers and father. As both my uncle live luxury life. I'm earning well but just as enough to feed my family. I have a son and worried about his future. With Regards, Manish Kumar