Kuśa (Kusa)was the eldest son of King Rāmacandra (Ramachandra), belonging to the Ikṣvāku (Ikshvaku) dynasty. Amūrtarayā (Amurtaraya) was one of the four sons of Kuśa.

Vāyupurāṇa(91.62)
Brahmāṇḍapurāṇa (Maharṣi)(2.66.32)