Cheating by paternal uncle

My grandfather purchased a property in my paternal uncle name in sep 1955 when he was three years old and reconvened it to the actual seller in the same year after three months I.e. in Dec 1956. After that my grandfather became sirdar of that land during consolidation and later became bhumidar by paying sanad. He also purchased another property in name of my paternal uncle but he became just major during the deed but the payment was made by my grandfather. Now after the death of my grand father and father my paternal uncle started claiming that property showing the deed executed.in his name and started saying the reconveynence deed was void as he was minor. He was always aware of that land belonging to my grandfather as he also did some regustered rent agreement with my grandfather for doing farming on that very land. The khatauni always had my grandfather's name recorded earlier as sirdar and later as bhumidar and afterwards me and my uncle became joint owner through paka 11. But my uncle has taken possesion and sold 80% of the property by showing his first deed. What should I do and what remedy do I have?