Uncle prepared forged will what action can be taken

sir, My father is two brothers, he was younger and was in service. .My uncle was residing at village. My grandfather resided with my father . Grandfather died in 1993 . As it was natural that he was elder in the family , my father had faith on him ,signed every document he presented before my father for signature. Now in 2016 while partition of the family it came to our notice that land is not divided equally between the two sons as they were the sole inheritors of the my grandfather property. My father's elder brother had prepared a forged will after death of my grandfather through which he transferred 11 more acres of land in his own name and remaining was divided between my father and uncle. It was a forged will and prepared after the death of my grandfather. What should I do now to get back the land?