Even though it is your great grandmother's property, it will not be considered as ancestral property since it has not descended from the patriarchal side.
It will devolve on the immediate legal heirs.
The property shall be divided into two equal shares, one for your grandfather and another share to his sister.
Upon your grandfather's intestate death, his share of property shall devolve again on his own legal heirs namely your father and his sister.
Now they both will be the absolute owners of their respective share of property.
The next generation, i.e., you or your siblings cannot claim any share in your father's share of the property as a right, at least not during his lifetime.
You can consult a local advocate on all such further issues.