Leda was seduced/raped by Zeus when he came to her in the form of a swan. Leda then gave birth to an egg. From it, it hatched the the twins Castor and Pollux who were often called "sons of Zeus" or the Dioscouri which means "the striplings of Zeus." Sometimes they were even called The Tyndaridae; "sons of Tyndareus." They went on the Quest of the Golden Fleece, took part in the Calydonian boar-hunt; and lastly they rescued Helen. When Castor died, Pollux prayed that to Zeus that he to would die. (except he couldn't because he was immortal!) Zeus then allowed Castor and Pollux to share immortality between them. The two were never separated again.

The Story of Castor and Pollux