Śrīmad-Bhāgavatam · Text 9.16.37
Who is speaking and story frame
एवं कौशिकगोत्रं तु विश्वामित्रै: पृथग्विधम् ।
प्रवरान्तरमापन्नं तद्धि चैवं प्रकल्पितम् ॥ ३७ ॥
evaṁ kauśika-gotraṁ tu
viśvāmitraiḥ pṛthag-vidham
pravarāntaram āpannaṁ
tad dhi caivaṁ prakalpitam
Viśvāmitra cursed some of his sons and blessed the others, and he also adopted a son. Thus there were varieties in the Kauśika dynasty, but among all the sons, Devarāta was considered the eldest.
Read Śrīla Prabhupāda's purport on Vedabase.io