Castor and Pollux in Wikipedia

(pronounced /ˈkæstər/; Latin: Castōr; Greek: Κάστωρ, Kastōr, "beaver") and Pollux (/ˈpɒləks/; Latin: Pollūx) or Polydeuces (/ˌpɒlɨˈdjuːsiːz/; Greek: Πολυδεύκης, Poludeukēs, "much sweet wine"[1]) were twin brothers in Greek and Roman mythology and collectively known as the Dioskouroi. They were the sons of Leda by Tyndareus and Zeus respectively, the brothers of Helen of Troy and Clytemnestra, and the half-brothers of Timandra, Phoebe, Heracles, and Philonoe. They are known collectively in Greek as the Dioscuri (/daɪ ˈɒskjəraɪ/; Latin: Dioscūrī; Greek: Διόσκουροι, Dioskouroi, "sons of Zeus") and in Latin as the Gemini (/ˈdʒɛmɨnaɪ/; "twins") or Castores (/ˈkæstəriːz/). They are sometimes also termed the Tyndaridae or Tyndarids (/tɪnˈdɛrɨdiː/ or / ˈtɪndərɪdz/; Τυνδαρίδαι, Tundaridai), later seen as a reference to their father and stepfather Tyndareus. In the myth the twins shared the same mother but had different fathers which meant that Pollux was immortal and Castor was mortal. When Castor died, Pollux asked Zeus to let him share his own immortality with his twin to keep them together and they were transformed into the Gemini constellation. The pair were regarded as the patrons of sailors, to whom they appeared as St. Elmo's fire...