Kitáb-i-Aqdas

Should the son of the deceased have passed away in the days of his father and have left children, they will inherit their father's share   ¶26

This aspect of the law applies only in the case of the son who predeceases his father or mother. If the daughter of the deceased be dead and leave issue, her share will have to be divided according to the seven categories specified in the Most Holy Book (Q and A 54).