Castor

Touched by so much love, Zeus let his son choose either to remain young forever and live among the gods or to give half of his immortality to his brother so together they shall spend one day in the underground kingdom of Hades and one day in Olympus to age and ultimately die. Without thinking, Pollux chose the second option and from then on wandered with Castor between Olympus and Hades. The brothers became the two brightest stars in the constellation Gemini.