7/12 entry my grandfathers name Lapse year 1975

My great grand fathers name was an agriculture land purchased by government for collage purpose but my great grand father die early edge my great grand fathers brother has total power his hand the money given to my great grandfathers brother name because my Grandfather was minor age leter 1962 an Agriculture land situated in Dhule Maharashtra it was purchased by my great grandfathers mothers name in the year 1962 my great grand father already died at that time My Great Grandfathers mother died in the year 1975 Taking advantage of time My Great grandfathers "Brother " adding his name whole property instend of adding my grandfathers joint name. Now My grand father , My father also died, Great grandfathers "Brother " also died in the year 1987 he has no child after his death his wife neme showing in 7/12 entry she died in the year 2017 but she gift whole property by "will" his brothers sons name.My mother chellenge in revenu offcie but the officer told from 1975 my grandfathers name left at that time after 40 years time limit law is thair My quation is how can get our rights in our anctral property please guide me