Property issues

Hi, My grandfather is 75+ years old ,he says his 3 acre agricultural land he wants to sell it,He also says it is his self acquired property so he can sell it to whoever he wants to ,my father is alcoholic and he doesn't care about all these but my mother who has worked and grown crops in that agricultural land and also cooked food to all labourers during crop seasons each year for 20+ years and after selling the Crops the money is deposited directly to grand father account, my mother still has not received any fruit from all these 20+ years of work ,she still has black beads Mangal Sutra around her neck,grand father and grandmother doesn't like my mother and they also used to put up his alcoholic son to beat the shit out of my mother out of nothing,can I being a grand son stop my grandfather from selling agricultural property as it is our only line of living ,with that we can grow something and live the life,we are very poor , agricultural land once sold cannot be acquired again by the likes of us.requesting could you please advise