SB 9.16.35
jyestham mantra-drsam cakrus
tvam anvañco vayam sma hi
visvamitrah sutan aha
viravanto bhavisyatha
ye manam me ’nugrhnanto
viravantam akarta mam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Thus the younger Madhucchandas accepted Sunahsepha as their eldest brother and told him, “We shall follow your orders.” Visvamitra then said to his obedient sons, “Because you have accepted Sunahsepha as your eldest brother, I am very satisfied. By accepting my order, you have made me a father of worthy sons, and therefore I bless all of you to become the fathers of sons also.”
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Of the one hundred sons, half disobeyed Visvamitra by not accepting Sunahsepha as their eldest brother, but the other half accepted his order. Therefore the father blessed the obedient sons to become the fathers of sons. Otherwise they too would have been cursed to be sonless mlecchas.