For Gemini and Virgo you are correct that the 7th house would be ruled by Sagittarius and Pisces, which are the two signs by Planet Jupiter. However Both the signs are very different in terms of their behaviour , characteristics and personality. Sagittarius is the Positive sign of Jupiter while Pisces is the negative sign of Jupiter. If you are not into astrology then you need to know that every planet except Sun and Moon has two signs in the Zodiac , one is a positive sign and other is a negative sign. One is a male sign and the other is a female sign. A male sign would have male qualities and a female sign would have female qualities. Male qualities would include aggressiveness, rigidity, stubborn while negative qualities would include being emotional, sentimental etc.
Another major difference between Sagittarius and Pisces is that Sagittarius is fiery sign while Pisces is watery sign.
These qualities of Sagittarius and Pisces would show in the spouse of Gemini and Virgo respectively, which would make them very different despite both signs being ruled by Jupiter.
Blessings,
Navneet Khanna
Astrologer