SB 9.8.14

yo ’samañjasa ity uktaḥ
 sa keśinyā nṛpātmajaḥ
tasya putro ’ṁśumān nāma
 pitāmaha-hite rataḥ
Synonyms: 
yaḥ — one of the sons of Sagara Mahārāja; asamañjasaḥ — whose name was Asamañjasa; iti — as such; uktaḥ — known; saḥ — he; keśinyāḥ — in the womb of Keśinī, the other queen of Sagara Mahārāja; nṛpa-ātmajaḥ — the son of the King; tasya — of him (Asamañjasa); putraḥ — the son; aṁśumān nāma — was known as Aṁśumān; pitāmaha-hite — in doing good for his grandfather, Sagara Mahārāja; rataḥ — always engaged.
Translation: 
Among the sons of Sagara Mahārāja was one named Asamañjasa, who was born from the King’s second wife, Keśinī. The son of Asamañjasa was known as Aṁśumān, and he was always engaged in working for the good of Sagara Mahārāja, his grandfather.