Castor and Pollux: the Twin Gods
The Disocuri were Castor and Polydeuces (or Pollux), the twin sons of Leda and Zeus and the brothers of Helen of Troy. Because Zeus came to Leda in the form of a swan, they are sometimes presented as having been born from an egg. Pollux was a formidable boxer, and Castor was a great horseman. Together, they were the "Heavenly Twins," often associated with the constellation Gemini.
Pollux was granted immortality by Zeus, but he persuaded Zeus to allow him to share the gift with Castor. As a result, the two spend alternate days on Olympus (as gods) and in Hades (as deceased mortals).
Bullfinch's Castor & Pollux
Temple of Castor and Pollux
Pictures and Drawings of Temple of Castor & Pollux
The Constellation of the Twin Gods
Macaulay, in his "Lays of Ancient Rome," thus alludes to the legend:
"So like they were, no mortal
Might one from other know;
White as snow their armour was,
Their steeds were white as snow.
Never on earthly anvil
Did such rare armour gleam,
And never did such gallant steeds
Drink of an earthly stream.
"Back comes the chief in triumph
Who in the hour of fight
Hath seen the great twin Brethren
In harness on his right.
Safe comes the ship to haven,
Through billows and through gales,
If once the great Twin Brethren
Sit shining on the sails."