Jason's father is invariably Aeson, but there is great variation as to his mother's name. According to various authors, she could be:
Jason was also said to have had a younger brother Promachus and a sister Hippolyte, who married Acastus (see Astydameia).
Persecution by Pelias
, king of Iolcos
, stops on the steps of a temple as he recognises young Jason by his missing sandal; Roman fresco
, 1st century AD.
Pelias (Aeson's half-brother) was power-hungry and sought to gain dominion over all of Thessaly. Pelias was the progeny of a union between their shared mother, Tyro ("high born Tyro"), the daughter of Salmoneus, and the sea god Poseidon. 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 still-born. Fearing that Pelias would eventually notice and kill her son, Alcimede sent him away to be reared by the centaur Chiron,; she claimed that she had been having an affair with him all along. Pelias, fearing that his ill-gotten kingship might be challenged, consulted an oracle, who warned him to beware of a man wearing only one sandal.
Many years later, Pelias was holding games in honor of Poseidon when the grown Jason arrived in Iolcus, having lost one of his sandals in the river Anauros ("wintry Anauros") while helping an old woman (actually the Goddess Hera in disguise) to cross. She blessed him for she knew, as goddesses do, what Pelias had planned. When Jason entered Iolcus (present-day city of Volos), he was announced as a man wearing only one sandal. Jason, aware that he was the rightful king, so informed Pelias. Pelias replied, "To take my throne, which you shall, you must go on a quest to find the Golden Fleece." Jason readily accepted this condition.