Maternal grandparents want to give their property. dispute b/w sons

This is about my mother's father property. My mother & father live with my maternal grandparents along with their son & his family. He & his wife wants to sell the property and wants ? or full share and tries to create nuisances everyday for selling the house and even tries to kill my mother & father but their no evidence to prove so that we can lodged a complaint. My maternal grandparents wants to give their property to my mother willfully because she takes care of her but his son don't do anything he lives here only for property.