Udayana is the son of king Arbhaka (Darbhaka) elonging to Śiśunāga vaṁśa. However in the engali edition of Viṣṇupurāṇa, the reading is Udayāśva (Udayswa).  King Udayana had a son called Nandivardhana.

Śrīviṣṇupurāṇa with Viṣṇucitti Comments(4.24.16-17)
Viṣṇupurāṇa(4.24.3)