Castor and Pollux (or in Greek, Polydeuces) were twin half-brothers in Greek and Roman mythology, known together as the Dioscuri. Their mother was Leda, but they had different fathers; Castor was the mortal son of Tyndareus, the king of Sparta, while Pollux was the divine son of Zeus, who seduced Leda in the guise of a swan.
In Latin the twins are also known as the Gemini or Castores, as well as the Tyndaridae or Tyndarids. The pair were regarded as the patrons of sailors, to whom they appeared as St. Elmo's fire. They were also associated with horsemanship, in keeping with their origin as the Indo-European horse twins.