Kastor and Polydeukes

Kastor and Polydeukes (or in Roman; Castor and Pollux, anglicized Castor and Polydeuces) are twin brothers in Greek and Roman mythology, known together as the Dioscuri or Dioskouroi that later formed the constellation of Gemini.

Their mother was Leda, however Kastor was the mortal son of Tyndareus and Polydeukes was the demigod son of Zeus. When Zeus seduced Leda in the form of a swan, Leda laid two eggs each producing two offsprings, from one egg was Kastor and Clytaemnestra and from the other egg was Polydeukes and Helen of Troy. Kastor had other sisters by Tyndareus and Leda: Timandra, Phoebe, and Philonoe.

In Latin, the twins are also known as the Gemini ("twins") or Castores, as well as the Tyndaridae or Tyndarids. Pollux asked Zeus to let him share his own immortality with his twin to keep them together, and they were transformed into the constellation Gemini. The pair were regarded as the patrons of sailors, to whom they appeared as St. Elmo's fire. They were also associated with horsemanship, in keeping with their origin as the Indo-European horse twins.

Genealogy

Lelegid/Lacadaemonid Genealogy in Greek mythology

Poseidôn               Lelex   Cleocharia                           Myles   Euhippe                         Clete   Eurotas     Zeús       Taygete                                                         Lapithes of the Lapiths   Orsinome           Sparta               Lacedaemon                                                                                                                           Acrisius of Argos   Eurydice               Amyclas   Diomede                                                             Zeús   Danaë                                                                                               Philomela   Cynortas       Argalus             Perseus   Andromeda                                                                                                             Gorgophone   Oebalus                                                                                                                                                             Hippocoon   Tyndareus       Leda       Zeús   Polycaste   Icarius                                                                                                                                                                     Castor               Polydeuces     Penelope   Odysseus of Ithaca                                                                                                         Agamemnon of Mycenae   Clytaemnestra           Helen   Menelaus                                                                                       Telemachus