Manavashrautasutra 11.8.10.10

11.8.10.10

dve kuryād ekaśrāddhe kuryād vā pṛthag anudiśyaikapiṇḍe dvāv anukīrtayet parigrahītāraṃ cotpādayitāraṃ cā tṛtīyāt puruṣāt /

One may perform two [offerings] in a single ancestral rite, or having designated them separately, he should recite two on a single ancestral ball—both the adopter and the progenitor—up to the third generation.