Property gifted through convence deed

Dear sirs In 2009 , I took loan from same relatives { they had applied for loan and drawn cash which was given to the buyer & my mother took loan from bank to purchase a piece of land. ( we are 03 brother (02 Married with children ) 01 unmarried brother and 01 unmarried sister. But due to some reason the land was registered in my fathers name. the source of income of my father were very limited( it can be proved) and now he has expired.but prior to his death he has discreetly made some gift deed for the subject land in favour of my sister. Since the motarable road to our old peice of land in (name of My mother) passes through this piece of land, we intend to take our right on the road at least if not the full land. request to reply the following plse : *can the gift deed be cancelled on any ground , like the property was not acquired by my father from his own money. How can he gift it ... *now my father has expired and the mutation of the same in favor of my sister has not been done, since the transfer has to be done during the life time of the done, can the gift deed be challenged. * can my son claim his right in the ancestral property. or any other way to go about this