Cancellation of land sale and deed of sale

An ancestral land, grand father get by partition from court in 1941, grand father died, but at the time of grandmother, my father, living the unblance life not as it expected from norma human being and not properly taken care of family, i.e. Mother and my sisters etc..sold the land without the consent of family members in or around of1980s and also enter into agreement to sale more..even my grand mother not consented at that time, my grandmother died in 1998, the agreement to sold between my father and others district court has decided that agreement was correct. ..now I can challenge the said agreement and its court order along with earlier sale deed in the ground of incompetent to contract..fraued etc..because at that time while entering entire agreement and sale deed no family members were consented..even my grandmother..and both the party I.e. My father and others were well aware that land belongs to my grandmother and it is an ancestral land so both the parties done fraud..kindly help and if possible provide me the references of similar cases etc..The matter known to me recently about the earlier sale of land during the proceedings of suit of challenging of agreement to sale by other party that is done by my father. I want to challenge the entire episode with my mother..