How to claim legal rights after death of father

My father had started the business of my grandfather. He worked in the business almost 20 years . After my fathers marriage my grandmother emotional blackmailed and snatched from my father and gave to my father's brother. Today they are saying that" yours nothing and your father didn't work . So that here is no share in the property . They are not giving our share and saying your father is no more so that here no share of yours. And the room in which me and my family are living ..'we have no receipt of the room .we have just 27 years of living proof of that room. And they are saying leave the room and go from here n we will just give you an enough amount to buy a 2 room flat . Otherwise they are not agreeing to give our share in property. " i want to know what should we do now ?