Castor and Pollux, whose astrological counterpart, Gemini, begins each year on 21 May, are important figures in Estruscan and Roman mythology and appear often in Italian art over the centuries. Stories of the twins Castor and Pollux, or Kastor and Polydeuces, came originally from Sparta. In Homer and in Hesiod they are the twin sons of Tyndareus and Leda, and the brothers of Helen of Troy.
In Roman tales Polydeuces is represented as the son of Zeus and Leda, and is immortal. When Kastor, the mortal son of Tyndareus, is fatally wounded, Polydeuces chooses to share his immortality with his brother, so that they both spend half their time below the earth at Therapne near Sparta and the other half with the gods on Mount Olympus. As the Dioscuri became identified with the constellation Gemini, they were regarded as protectors of travelers, especially sailors.
In Roman religion the worship of Castor and Pollux was introduced with the founding of the city. Their temple at Rome was decidcated by the dictator Aulus Postumius during the battle of the Romans against the Latins at Lake Regillus in 496 BCE. The story was that they then fought at the head of the Roman army and after the battle brought the news of the victory to Rome. The twins were seen watering their horses at the Lacus Iuturnae, a fountain in the Forum, and their temple was erected on that spot, beside the shrine of Vesta. The Roman equites regarded the brothers as their particular patrons. The common oaths mecastor and edepol, based on their names, are evidence of their popularity.
Reference:M.C. Howatson,ed. “Dio’scūri.” In The Oxford Companion to Classical Literature. Oxford: Oxford University Press, 2011. http://www.oxfordreference.com/view/10.1093/acref/9780199548545.001.0001/acref-9780199548545-e-1058.
Etruscan inscription to the Dioskouroi as “sons of Zeus” on the bottom of an attic red-figure kylix, c. 515 BCE. The Metropolitan Museum of Art, Nr. L.2008.1.1.
Castor and Pollux, Palazzi del Campidoglio. Rome, c. 1585. Photo: Wikimedia Commons.
Pair of Roman statuettes, c. 300, depicting the Dioscuri as horsemen, with their characteristic skullcaps. The Metropolitan Museum of Art, Nr. M.1957.3.
Temple of Castor and Pollux, Forum Romanorum, Rome, ca. 7 BCE. art History Survey Collection, ArtStor.
Intaglio of Castor and Pollux, c 300 BCE. Sapphirine, mounted gold. The John and Mable Ringling Museum of Art, Nr. SN1435.91.
Mausoleum Cenotaph Of Julii, Roman bas-relief showing the legend of the hunt for the Calydonian Boar, conducted by Meleager, with Castor and Pollux shown on horseback. First Century BCE. St. Remy, France Shmuel Magal, Sites and Photos, Nr. R150600112.
Further Reading: Jan Zahle and Siri Sande. The Temple of Castor and Pollux III: The Augustan Temple. Rome: “L’Erma” di Bretschneider, 2008.
Henry John Walker. The Twin Horse Gods: The Dioskouroi in Mythologies of the Ancient World. London: I.B.Tauris, 2015.