Choosing a Zodiac sign does not change personality, but Sims with compatible signs get a small relationship boost.

Zodiac Sign	Compatible with
Aries	Gemini, Leo, Sagittarius, Aquarius
Taurus	Cancer, Virgo, Capricorn, Pisces
Gemini	Aries, Leo, Libra, Aquaries
Cancer	Taurus, Virgo, Scorpio, Pisces,
Leo	Aries, Gemini, Libra, Sagittarius
Virgo	Taurus, Cancer, Scorpio, Capricorn
Libra	Gemini, Leo, Sagittarius, Aquarius
Scorpio	Cancer, Virgo, Capricorn, Pisces
Sagittarius	Aries, Leo, Libra, Aquarius
Capricorn	Taurus, Virgo, Scorpio, Pisces
Aquarius	Aries, Gemini, Libra, Sagittarius,
Pisces	Taurus, Cancer, Scorpio, Capricorn,