The star constellation Gemini or Twins represents two brothers, Castor and Polydeuces or in Latin, Pollux. The twins are actually half brothers. Their mother was Queen Leda of Sparta. Pollux's father was Zeus. Pollux was immortal. Castor was mortal and his father was King Tyndareus. Castor could die though, but Pollux could not.
The Twins took part in many heroic adventures, but they never, ever allowed themselves to seperate from each other. When it was time for Castor's impending death, Pollux asked his father if he could die with him so they could be together in death. Zeus let them share Pollux's immorality and eternal life. In return he would also have to share Castor's mortality and death. So, Pollux and Castor would forever have to alternate between light/life and dark/death. The brothers would forever spend one day on Olympus with Zeus and the next day with the underworld realm of Hades.
They say Pollux the star is much brighter than Castor, but Castor is more interesting because it is a multiple star system. A multiple star system is when a group of several bordering stars apparently rotate about a single gravitational center. The Castor is the magnitude of 1.93 and is 52 light years distance. The Pollux star is the magnitude of 1.16 and a distance of 33.7 light years away. Magnitude means how bright stars stars are. Pollux was the brightest star.