Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 9: Conversation Between Sumantra and Daśaratha
Text 1.9.3

कश्यपस्य तु पुत्रोऽस्ति विभण्डक इति श्रुतः।
ऋश्यशृङ्ग इति ख्यातस्तस्य पुत्रो भविष्यति॥

kaśyapasya tu putro ’sti vibhaṇḍaka iti śrutaḥ
ṛśyaśṛṅga iti khyātas tasya putro bhaviṣyati

kaśyapasya tu = Kaśyapa has; putraḥ asti = a son; vibhaṇḍakaḥ = Vibhaṇḍaka; iti śrutaḥ = known as; ṛśyaśṛṅgaḥ = Rśyaśṛṅga; iti khyātaḥ = known as; tasya putraḥ bhaviṣyati = He will have a son.

Kaśyapa has a son known as Vibhaṇḍaka. He will have a son known as Rśyaśṛṅga.