Sale of agricultural land

Case Detail: My grand father was a Zamindar in Mirzapur ,Uttar Pradesh and was owing around 300 Bigha land (agricultural and other land ) , and died in the age of around 50 years and leave behind wife , 2 sons and 1 daughter. During that time my father was studying in class 12th (age around 15-16 years) , and this time was after independence of India and land were acquiring by the GOI through custodian due to abolish system of Zamindari. My father through court of law was able to save Agricultural land around 25 Bighas, and mutation was filed in land record as 5 Bigha in her mothers name, 10 Bigha in Elder son name, and 10 Bigha in younger son name. My uncle was unemployed and started selling his land at the time for requirement of money and sold all land in his name. My grand mother ( age around 80 years) was alive and my uncle convinced her to sell her property without my fathers knowledge and kept amount with him. My grand mother died and on her remaining property my fathers name and my uncle name registered in record as inheritance. After 15 years,my father died recently and my uncle saying that he has right of half of the property and harassing us and selling half of his portion again. Kindly advise.