The daughter's son offers funeral cakes to his own father and the father of his mother. Hence, for the ends of justice, there is no difference between the son and their daughte son.
ददाति हि स पिण्डान् वै पितुर्मातामहस्य च। पुत्रदौहित्रयोरेव विशेषो नास्ति धर्मतः॥