The Gemini are two twins, Castor and Polydeuces (Pollux) in Greek mythology; the Dioscuri. They are sons of Leda, a daughter of Thestius and the wife of Tyncareus, and Zeus, the god of the heavens, and the brothers of Helen of Troy. Each of the twins had a special talent: Polydeuces was a very good boxer, and Castor was a talented horseman. They had many adventures together.
When their sister was kidnapped (during the Trojan War), they went and rescued her. They also helped Jason on his quest for the Golden Fleece. However, Castor was later killed when the nephews of Leucippus, Idas, and Lynceus fought them in a battle.

Later, when Zeus offered to give Polydeuces the gift of immortality, Polydeuces remembered his slain brother, Castor. Because of this, Polydeuces asked Zeus if he could share the gift of immortality with his brother. Zeus agreed and they spend every other day either as a god on Olympus or in Hades as a mortal who had passed away.