Aja was the descendant of Nimi of the Solar Dynasty (Sūryavaṃśa; Suryavangsha). He is the son of Ūrdhvaketu Janaka (Urdhvaketu Janaka) and father of Purujit Janaka.

Bhāgavatpurāṇa Vols. 1-12(9.13.22)