1. Your father can file a partition suit to divide the property left behind by his father into equal number of parts equal to the number of legal heirs to succeed to your deceased grandfather's estates and to allot one such equal share with separate possession.
He should do it immediately if he wants any relief out of this situation.
If there are only two legal heirs to your grandfather, then the entire property shall be divided into two equal shares and your father would be allotted with one such share.
2. It is a misguidance.
Do not do any such thing in haste, it may draw an adverse impact.
He has to file a suit for partition and he can sell his part of proeprty only after the court allocates his share in the property by a decree or judgment in the partition suit.
Please remember that this is not an ancestral property.