1. When the properties were owned by your grand father and grandmother, those were not ancestral properties,
2. To call a property an ancestral property, there shall have to be free flow of uninterupted title for 4 generations i.e. from great grandfather to great grandchildren,
3. So, in your case, you have no right to claim any share in the property during the life time of your grand father and grand mother & they are entitled to decide as to whom they will gift their properties,
4. After their demise intestate, the property will be inherited by your father and chacha and till their demise intestate, you won't have any claim on the said property.