In Greek and Roman mythology, Castor and Pollux or Polydeuces were twin brothers, together known as the Dioskouri. Their mother was Leda, but Castor was the mortal son of Tyndareus, the king of Sparta, and Pollux the divine son of Zeus, who raped Leda in the guise of a swan. Though accounts of their birth are varied, they are sometimes said to have been born from an egg, along with their twin sisters and half-sisters Helen of Troy and Clytemnestra.