Rights of the step mother on the inherited ancestral property

My grand father who passed away many years ago registered a home to my father. we are 3 children and all are adults. My father fought with my mother and married another woman(not sure if he has a marriage certificate but he has pics and videos). my mother never received any documents that states that she is legally divorced from my father. Some times my father claims that he took a signature from my mother by tricking her for the divorce aceeptance. My question is do the second wife of my father will have legal rights on the property that we inherited from our grand father? Can my father sell the property without our permission? What is the right way to deal this?