How will property be transferred after grandfathers death

My grandfather having five children .All children are married and setteled .out of that elder son of grandfather came to rest of the children and ask signature on some papers 10 years ago and asking that he want to take some loan for reneuation and all are signed at there home premises.after a long period we got to know that the room of grandfather means ownership of room he transferd to himself by using that signature.now the grandfather is died and his elder son is staying with that room ..now the question is can we go with any legal advice ...that how the property can transferd to him...or else we can go head with RTI law.