1. Ancestral property is one which has traversed for four generations without division and is intact. From great grand father(paternal side) to great grand children(paternal side). I am quoting the definition "Property inherited up to 4 generations of male lineage (i.e., father, grand father, etc.) is called as ancestral property". The right to a share in such a property accrues by birth itself, unlike other forms of inheritance, where inheritance opens only on the death of the owner.
2. In the instant case(as per your narration), your great grand father divided the property between your grand father and his brother, therefore in your grand father's and his brother's hands, it is their self acquired property. Since it is the self acquired property of your grand father, he has the absolute right to deal with the property in any manner he likes, including gifting the property to anyone or selling the property and he may do anything with the proceeds as he likes during his lifetime.
3. Being the owner of self acquired property, your grand father can execute a 'WILL' and bequeath the property to anybody, including your Father and/or Uncle. In case he dies intestate(without executing a "WILL"), then your father along with other legal heirs get equal share in the property.