Wikipedia
Yayati was a Puranic king and the son of King Nahusha and his wife asokasundhari. He was one of the ancestors of Pandavas. He had five brothers: Yati, Samyati, Ayati, Viyati and Kriti. Yayati had conquered the whole world and was the Chakravartin Samrat (Universal Monarch or World Emperor). He marries Devayani and takes Sharmishtha, daughter of king Vrishparva and maid of Devayani as his mistress on her request. Devayani was the daughter of Shukracharya, the priest of the Asuras (the demons). After hearing of his relationship with Sharmishtha, Devayani complains to her father Shukracharya, who in turn curses Yayati to old age in the prime of life, but later allows him to exchange it with his son, Puru. His story finds mention in the Mahabharata- Adi Parva and also Bhagavata Purana.