Matsya Purana — Soma
एते तु पितरो देवा मनुष्याः पितरश्च ये पिता पितामहश्चैव तथैव प्रपितामहः //
ete tu pitaro devā manuṣyāḥ pitaraśca ye pitā pitāmahaścaiva tathaiva prapitāmahaḥ //
These indeed are the Pitṛs: both the divine Pitṛs and those among humans who are called “ancestors”—the father, the grandfather, and likewise the great-grandfather.
This verse does not discuss Pralaya; it defines who is counted as a Pitṛ (ancestor), emphasizing the ancestral line up to the great-grandfather and acknowledging divine Pitṛs as well.
It supports the householder’s dharma of honoring ancestors through śrāddha and tarpaṇa by clarifying the primary ancestral recipients—father, grandfather, and great-grandfather—alongside the broader category of divine Pitṛs.
The significance is ritual rather than architectural: it frames the eligible Pitṛs for offerings in ancestral rites (śrāddha/tarpaṇa), grounding correct ritual intent and recipient identification.