The symbol for Gemini represents a companion. It also shows the Babylonian Great Twins, Greek Castor and Pollux, or a Roman figure II that stands for the number 2. This is a constellation that looks a lot like two twins holding hands, and the symbol is to present the unbreakable bond of two brothers.
The sign of Gemini is ruled by planet Mercury that got its name by the Roman god of communication, eloquence, travelers, boundaries, trickery, luck and thieves. He was also the guide of souls to the underworld. Its Greek counterpart is Hermes, a messenger, quick and cunning, moving swiftly through the worlds of mortal and divine
The symbol for Mercury is consisted of a circle and a cross below it, same as Venus, only with a crescent at its top. Crescent denotes the mind, circle the spirit and cross the physical matter. This symbol shows the divine nature of the mind (Gemini) and its physical one (Virgo). The “horns” made by the crescent are also linked to the winged hat that Roman god Mercury used to wear. This god was also symbolized by a caduceus – a staff with two snakes wound about it.