Gemini is one of 48 constellation set up by Claudius Ptolemy. It has an area of 514 square degrees and 118 naked-eye stars. ecliptic It is one of the twelve constellation.

The star Pollux in the west is a first magnitude star and Castor in the east is a bright second magnitude star.

In Mesopotamia, the head of Gemini was called the big twin and the center the small twin. In Greek mythology, they were the Castor-Polydeuces brothers, princes of Sparta.

Leda, the wife of the ancient Spartan king Tyndareios, was so beautiful that Zeus took a liking to her and transformed himself into a swan so that he would not be recognized by the king. Leda then laid two eggs, giving birth to the brothers Kastor and Polydeuces and the sisters Klytimnestra and Hellene.

Castor was the son of a king and an ordinary mortal, while Polydeuces is said to have been immortal because of the blood of Zeus. When his brother Castor lost his life, legend has it that Polydeuces was so saddened by the parting that he asked Zeus to lift them both up into the sky and they became constellation.

[Source of story.
Hoshi no Bunka Rekishi Jiten (Encyclopedia of the Cultural History of the Stars), Hakusuisha, Inc.
Zenten constellation Encyclopedia, Kawade Shobo Shinsha (February 2011)