In one's family one can count back four or five generations - to one's great-grandfather or even one's great-grandfather's father - but since the Lord mentions twenty-one forefathers, this indicates that the benediction expands to other families also

Expressions researched:
"In one's family one can count back four or five generations—to one's great-grandfather or even one's great-grandfather's father—but since the Lord mentions twenty-one forefathers, this indicates that the benediction expands to other families also"

Srimad-Bhagavatam

SB Canto 7

The word triḥ-saptabhiḥ means seven multiplied by three. In one's family one can count back four or five generations—to one's great-grandfather or even one's great-grandfather's father—but since the Lord mentions twenty-one forefathers, this indicates that the benediction expands to other families also.

SB 7.10.18, Translation and Purport

The Supreme Personality of Godhead said: My dear Prahlāda, O most pure, O great saintly person, your father has been purified, along with twenty-one forefathers in your family. Because you were born in this family, the entire dynasty has been purified.

The word triḥ-saptabhiḥ means seven multiplied by three. In one's family one can count back four or five generations—to one's great-grandfather or even one's great-grandfather's father—but since the Lord mentions twenty-one forefathers, this indicates that the benediction expands to other families also. Before the present family in which one has taken birth, one must have been born in other families. Thus when a Vaiṣṇava takes birth in a family, by the grace of the Lord he purifies not only that family but also the families of his previous births.