Must the heirs of a deceased son return what their father inherited from their grandmother, or can the grandmother change her intention from an inheritance to a gift for her son's children?

It is permissible for a person to divide his wealth among his heirs during his lifetime as a gift, and he is obligated to be just among them. If the son receives his share from this division before his father's death, this share becomes his property and transfers to his heirs after his death, including his mother who inherits one-sixth. If the son dies after receiving his share, this share is not returned to his mother or siblings; rather, it becomes an inheritance to be divided among his heirs. The grandmother (the deceased's mother) may relinquish her share (one-sixth) to the deceased's children if she wishes.