Who is legal heir to my grandfather land my mother or me

My grandfather owned a land from the government for agreculture use. My grand father has 5 sons i am the elder son of J mallaiah who is elder son to my grand father both i.e., my grand father and my father died without saying any thing about that land.While house shifting we found some land related documents in my father's private shell. Our uneducated family members are blindly concerned a broker who is well know for dealing with unknow lands with 50% share after a long discussions and obtaining trust (he is related to our relegion) they have provided land documents to him Not only that every body has signed in black paper the broker took advantage by that and now claiming for entire land with that signatures.. now he is insisting us for registration. What I wanted to know is who is legal heir for our grandfather property my mother and rest of family members ( remaining sons out of five sons) My father brother's don't need that land but I wish to build a house in that land what should I do to preserve our grand father's land please do us a favor in this issue with an ultimate solution