How to claim property possessed by brother illegally

My late grandfather has three son. My father is eldest followed by two uncles. My grandfather was a farmer. My father was working in a town and retired around 1995. My father sent money to Village to my grandfather. My grandfather bought so many plots on his name while he bought one plot on my father's name. My younger uncle any how convinced my grandfather and transfered 40 % of land on her wife name. Presently 100% land is captured by my younger uncle. Some old people know that my father had given money to buy the land. But we don't have any money order slip. What should I with my father can do to take 1/3 rd land from my younger uncle.