Son of Bhrigu and his wife Puloma, married to Sukanya, the daughter of King Sharyati.
Chyavana was an old ascetic. One day the Ashvin appeared and courted Sukanya. She chose Chyavana. The Ashvin then rejuvenated Chyavana.
For the story visit
https://www.vyasaonline.com/2018/04/25/sukanya/mahabharata