Agricultural land dispute

Immediately after my grandfather's death, my uncle decided to go separate. Land was divided equally between my father and my uncle. Uncle being a learned man, registration was done immediately. We got two separate booklets (Khate Pustika) containing a copy of the record of rights, one for my father one for my uncle. This was 47 years ago. Now my father and uncle is dead. My cousin comes to me now and says his father(my uncle) never got the right share of land. Its been almost 47 years, my father was a farmer and we have worked hard and developed our part of the land. He has sent legal notice through the Talathi (Tehsildar) office and demands part of land from my fathers share. My cousin is a powerful man, I believe he has bribed the Talathi officer. Talathi officer is not cooperating with us. There are some continuous plots of land where the 7-12 of land(record of rights) contains names of both families - my father's heir and uncle's heir. The division of such plots was done verbally. We are fine with the division but again we have developed our part, the other one looks barren. I would like to know if he can make such a claim after so many years? What to do if there is no cooperation from govt. officers? Please advice me how to deal with this situation. I am a retired person, back to farming. Regards..