Aja was the son of a king called Jahnu. Aja’s son was Ushika. Ushika prayed to Indra for a son, and Indra himself was born as Ushika’s son Gadhi. Gadhi had a daughter called Satyavati, who got married to Richika. According to Mahabharata Shantiparva Chapter 49, their son was Jamadagni, father of Parashurama.