What is my right in this property?

My maternal great grand mother had 4 children 1) my grand father,(G1) younger brother(G2) & two sisters (GS1&GS2) . My grand father had 4 children My mother (M) +2 sisters(A1& A2) & my uncle(U). My grandfathers two sisters had 2 sons (U1&U2) one each. When grandfather died through an agreement reached among them the sons of the two sisters decided to give their assumed share of property one to my Grandfather (G1) and the other to his younger brother(G2). This was in turn registered in my uncles name one share free of cost and the other share by paying Rs 9750/- to (G2). MY uncle (U) had no means of income at that time as he was a student and he prevailed upon the elders and got the property registered in his name without any of the other major sibilings or my grandmothers name included in the sale deed as against the assumption that he would do so on recieving the money from my grandmothers siblings in lieu of her share of property. He now sights that the properry is in his name and doesn't want to part with any of this and he also wants a share in the property of my grandfather.