Sir, My father was opened a Company in 1996, in that company my mother was a partner 25% my grand fa

Sir, My father was opened a Company in 1996, in that company my mother was a partner 25% my grand father was partner 50% and my father was partner 25%. some bad circumstances my father give out my mother from home in 1997, but a company and partnership was not terminated, in that company have a 47000 Sq. Ft. land, after my father give out my mother from home he was also go away from home, after that my grand father was sold a lend to other person without my mother or my father's signature. so i need help form you sir, how can I cancel a fraud sell agreement My mothers age is 56