Pelias was a son of Tyro by either her husband Cretheus, King of Iolcus or her lover Poseidon. Pelias was reportedly a twin brother of Neleus, King of Pylos.
In their youth, Pelias and Neleus are credited with rescuing their mother from cruel captivity in the hands of Sidiro, a woman who hated her. When Cretheus died, Aeson his eldest son rose to the throne. Pelias was power-hungry. He proceeded to depose and imprison Aeson. He claimed the throne for himself and exiled his siblings.
Years later, Jason, son of Aeson claimed the throne as his birthright. The aging Pelias decided to set an impossible task for this claimant: to go fetch the Golden Fllece from Colchis (modern Georgia). Jason set sail with his Argonauts. He returned with Medea. Her schemes soon resulted in the death of Pelias. She reportedly convinced Pelias' own daughters to slay him, claiming it was needed to rejuvenate their elderly father.