In astrology, a planet's domicile is the zodiac sign over which it has rulership. The planet said to be ruler of Gemini, or those associated with Gemineans, is Mercury. The term domicile also applies to the House in which a planet rules. Domicile is from the Latin domicilium whose root means house. Mercury has its Domicile in both the 3rd and 6th Houses of one's natal chart.
Gemini, which is Latin for twins, has taken on many identifications and meanings through the ages. Gemini is most commonly understood to represent the twin brothers Castor and Pollux in Greek mythology who were fraternal twins, born of the same mother, but having different fathers. Castor and Pollux are also the names of the alpha and beta stars of the constellation Gemini. Hyginus, as well as Bode's Uranographia, offers an alternate interpretation of the two figures as being Apollo and Hercules. The Tarot card associated with Gemini is "The Lovers", which portrays Adam and Eve. Adam and Eve are thought to have been created at the end of the age of Gemini—the inseparable figures being an allusion to the beginning of mankind.
There are many variables in the astrology chart that determine compatibility of individuals. The position of the Sun, the Moon, the planets and the aspects they form with each other are assessed by astrologers before judgment on compatibility is made. The signs listed as compatible with Gemini do not reflect an individual profile or individual reading as interpreted within astrology, but rather reflect a general guideline and reference to compatibility as dictated by variables such as Qualities and Elements within the Zodiac. The branch of astrology dealing with interpersonal compatibilities is called synastry.
^Mayo, Jeff (1979). Teach Yourself Astrology. London: Hodder and Stoughton. pp. 38–41. ISBN0340277440.