How to get grandfather properties grandmother remarried afterwards

Please suggest me When my father age was 6-8 year my grandfather was dead. After grandfather dead my grandmother get married to some on e and left my father .my father sister take responsibility of my father.after 15_16 year later my father's came in other states after long time when we go to our home means grandfather home for our property my grandfather brother and their children are telling that there is nothing for you. There in no property . But my father know there property. But they are saying that this is there property .Now how we get our property