1. It appears that your grand father got these proepeties from his father who got this after partition.
2. In that case if your father got the land on partition among his brothers then the same would be treated as his self acquired proeprty and hence he can deal with it in any manner he wishes.
3.However of your father got this properties from his father without partition then the same would be ancestral proeprty.
3.on that event you to stop him from transferring your du share to others cna file a suit for partition to claim your share and seek injunction to stop him from further selling his lands.