Sale of a jointly owned property without specific division

There is a joint property bought by my father and his mother in law together but they do not specifically mention the share that each has in the property . My father has built a house in his half share leaving the remaining land .Since both the owners have expired, now i live with my family in the aforesaid property. As my brother wants to start a business he is now asking me to sell the unoccupied land and settle his share.Now my question is 'can i sell the land without the consent of the heirs of my father's mother in law?' ( My father's mother in law has got 4 sons and a daughter i.e my grandmother) Or 'Can i sell the house in which we live without their consent?' (Since there is no mention about the share by the owners in the deed) Many thanks.