My grandfather has purchased 1 room in a slum via pagri system. In 2005 he made a gift deed for my f

My grandfather has purchased 1 room in a slum via pagri system. In 2005 he made a gift deed for my father saying now no other siblings will be a part of it. Now since 2005 my father is the owner of this property & all rent receipts, electricity bills are in my father's name. Now suddenly in 2015 my grandfather is asking my father to sell this property & make 3 parts. 1 for grandfather & other to for my uncle & father. We don't want to sell this. please advice.