Does the son of a brother who died before his father and grandfather inherit from the estate of the father and grandfather after their deaths?

Your nephew does not inherit from your grandfather's inheritance due to the presence of a closer heir, who is your father. He also does not inherit from your father's inheritance if your father has a direct son. The law of compulsory bequest (al-wasiyya al-wājiba), which mandates a share for the grandchild as if their father were alive, has no religious basis.