Sale of land through General Power of Attorney

Dear Sir/Madam, My Father in law had 2 acres of land which he has done GPA to person A. Note only signatures of him were taken and no where the signatures of his spouse and his daughter were not involved. He was under some family pressure and drink addicted and he did that. We are under estimation that the land was registered to A and we left hopes. It was 10 years back. Once in a while A gave us some money through a mediator for the land. Recently i have checked the pahani's and it was like the land is still on the name of my father in law. Whatever the land that was purchased by A and the price offered is peanuts when we compare it now. Is there a possibility that i can still name my mother in law as successor of the property as my father in law expired. Does she have legal rights to dispose the property to someone else as we feel cheated that the amount paid was not up to the rates existing now.