The twins were Castor and Polydeuces (Pollux). Together, they were known as the Dioscuri. Their sisters were Helen and Clytemnestra. They were the sons of Leda and Zeus and Tyndareus. Castor and Pollux were half-brothers. Leda was married to King Tyndareus of Sparta. At this time, she was also seduced by Zeus, so the father's of both children were uncertain. The Discouri were inseperable and grew closer with age.
Castor was a famous horsetamer and Pollux, a superb boxer. When Castor was killed during a battle, Pollux was inconsolable and gave up his own life to be with his brother. Zeus rewarded their love by placing their images among the stars, where they shine side by side. Two lines of stars makes up this constellation, and two bright stars at the top of each line represent Castor and Pollux's heads.