Stories about brothers?

Castor and Pollux, the brothers of Helen of Troy. One was the son of Zeus and the other was mortal, supposedly they hatched from eggs laid by their mother Leda, who made love to the god in his disguise as a swan. Supposedly the brothers were so inseparable that they ended up sharing the immortal soul of the god-born one (forget which) after death, spending half their time in Hades and the other half in Olympus.