According to Bhāgavatapurāṇa (Bhagavatapurana), Raya was the son born of the womb of Urvaśī (Urvasi), and sired by Purūravā (Pururava). Eka was the son of this Raya.

Bhāgavatpurāṇa Vols. 1-12(9.15.2)