As far as I know, the only life that has been mentioned is of the sages Nara Narayana, though the story of these two sages itself seems quite symbolic. So, possibly what Sri Krishna is hinting is that they have partnered together in a number of lives as the human instrument and the Divine Representative. This seems more likely since the Bhagavat Gita has been delivered by Sri Krishna in a supernormal Superconscious state where He mentions even about giving the Yoga to Vivaswan, the Sun god.
Affectionately,
Alok Da


