Ancestral Property Issue

If my Grandfather had made registry of our ancestral land to one of my uncle's wife without telling my father and now my uncle opened up a HP Petrol filling station in my village on that land. So, I want to know whether my father lost his share in that ancestral land or he's still a shareholder in that land. It's nearly 15 years ago and still they're not returning our share's land or giving another piece of land in place of that. What we've to do now.