The Disocuri were Castor and Polydeuces (or Pollux), the twin sons of Leda and Zeus and the brothers of Helen of Troy. Because Zeus came to Leda in the form of a swan, they are sometimes presented as having been born from an egg. Pollux was a formidable boxer, and Castor was a great horseman. Together, they were the "Heavenly Twins," often associated with the constellation Gemini.
Four episodes from their careers are most notable.
- After Theseus kidnapped their sister Helen and carried her off to Aphidnae, Castor and Pollux rescued her; they also abducted Theseus' mother, Aethra.
- Later, the twins accompanied Jason on the Argo; during the voyage, Pollux distinguished himself by killing the belligerent king Amycus, who challenged him to a boxing match.
- When Peleus attacked and laid waste to Iolcus, in revenge for the evils done to him by its queen, Astydameia, the Dioscuri assisted him.
- Castor and Pollux also abducted and married Phoebe and Hilaeira, the daughters of Leucippus; Castor was then killed in a battle with the nephews of Leucippus, Idas and Lynceus.
Pollux was granted immortality by Zeus, but he persuaded Zeus to allow him to share the gift with Castor. As a result, the two spend alternate days on Olympus (as gods) and in Hades (as deceased mortals).