I slightly differ to opinion of @ Stanly.
It is not clear if grand father was a Hindu. It is also not clear how the grand father got the property. However assuming this is question relating to Hindus rights below are some of the legal positions concerning Hindus;
1. If the property of the grand father was his "self acquired" property then this property shall devolve to all his legal heir if he died intestate. The queriest has not mentioned if grandfather alive or died interstate which is also important consideration.
2. Now if the property of the grand father was his "self acquired" property then this property shall devolve to all his legal heir if he died "intestate" that includes his father.
3. Well the grandson is not considered "legal heir" if his father is alive in para 2 scenario, in case the father of the grandson died before the death of grand father then the grandson being son of the predeceased son can get the share in the property which his father would have got, sharing that share along with his mother i.e. widow of his father. It is not made clear by the queriest if his father alive.
4. The grandson could also get his share in the property if it was a "Hindu Ancestral Property", i.e. originally owned by the great grand father, passed to the grand father down the line up to the present grandson who would be the fourth generation to enjoy this property, in this case if it is Hindu Undivided family property (HUF) a share could be claimed by the present grandson being a "Coparcener by birth" in the Hindu Joint family. The queriest has not clarified the nature of the holding.
A. Grand father can do anything that he wants with his “self-earned” property if it was his "self earned" property. This point whether the property was self earned also not clarified by queriest which is also important consideration.
B. However, the grand father can even give it to some strangers (without giving anything to any of his children i.e. father and grand children) or to a Trust or can even debar all heirs during his life time still none of the heirs can question his actions or demand any share whatsoever from the said property including grand son as in the query. If the queriest says the grand father has debarred then it should be his duty to clarify if even grand children were also debarred from such debarments?
In nutshell, few more clarity needed about the property first then property rights of Hindus comes into picture before jumping guns and applying them to claim property rights under DV Act are some of my views for a crude reason now-a-days DIL's are becoming more empowered on property matters when she has custody of children and using it to mould laws of Hindu Successions and demanding them to include into DV The Act as some sweeping interpretation least now some Court creats a precedent under DV Act on raised incomplete query hence I prefer cautious steps once I hear DV the Name!