Ancestral property dispute

My grandfather(alive) acquired his property from his father(not alive) who bought that from his earnings. My grandfather has two sons and three daughters, all married and all have children. My father is younger son. Now my grandfather has been brainwashed by my father's brother and he wants to give all the property to him without giving anything to his any remaining child, i.e my father and my father's sisters. So I want to know the following things: 1. Can we recognize the property as ancestral ? 2. Can my grandfather give his property(from his father) to anyone without consent of all his children with the help of any will or etc? 3. If yes, can I do anything to stop that? 4. If no, then who can file a petition in this case, me or my father ? 5. Can my father's sister's children claim on that property or only my father's sisters can do that? 6. If my grandfather pass away without any will in future then please answers my above question in that case too. 7. If my grandfather pass away with a will in future in which he give all property to my father's brother then please answers my above question in that case too.