بسم الله الرحمن الرحيم
(Fatwa: 894/831/SD=9/1438)
If your father is alive then he alone is the owner of all his property. There is no share of any of his heir in his property before his death. He has full right in his property to use it as he wishes. During his lifetime if he wants to give something to his Nawasa and Nawasi (grandchildren) then he may give to them. Yes, after his death in the presence of his children, the Nawasa and Nawasi will get nothing.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband