In Greek mythology, Castor and Pollux were twins with different fathers, and were brothers of Helen of Troy.
Leda daughter of Thestius and Laophohte or Eurythemis or Deidameia: she was Queen of Sparta, with her husband Tyndareus she had Castor with Zeus she had Pollux - though the boys are twins (born at...
if you're referring to their zodiac sign/constellation for Gemini its: II
Castor and Pollux are the roman name as well as their Greek name
Gemini