Property of grand father to grand son

We have a landed house which is bought by my grand father. My grand father has 3 kids, 2 sons and one daughter. Elder son is not married and he is alive. My dad is the younger son and he was given a part of land from the same land to construct house. My dad has constructed house and elder son is living in the house constructed by my grand father. One daughter of my grand parents who is younger to both sons, was given a land from other area which she disposed immeditately on getting from her parents. Now apart from the portion given to my dad, rest of the area(Land and a house) is in the name of my grand father. Few years back my dad's sister also joined with elder son and both are residing in the house of grand parents. Since elder brother is not married and the property of my grand parents is still in their name, as grand parents are not alive. Now who is eligible to have the right on the property. Is it the grandsons or the elder brother and younger sister. Younger sister has one son and my dad has 2 sons which is me and my younger brother.