In a bitter feud, he overthrew Aeson (the rightful king), killing all the descendants of Aeson that he could. He spared his half-brother for unknown reasons.

Aeson's wife Alcimede I had a newborn son named Jason, whom she saved from Pelias by having female attendants cluster around the infant and cry as if he were stillborn. Fearing that Pelias would eventually notice and kill her son, Alcimede sent him away to be reared by the centaur