Not exactly a thematic line, but Mythic Legions does offer a centaur
Aside from a water jug for Aquarius I think you could find a figure for all twelve signs in Mythic Legions depending on how literal you want the interpretation
-Capricorn: Goat Man’s upper torso on fish lady’s tail
-Scorpio: the Scorpion thief
-Sagittarius: the centaur
-Libra: Illythia
-Virgo: just pick a random lady
-Leo: the Big Lion man
-Cancer: the Big Crab man
-Taurus: pick your favorite Minotaur
-Ares: use the add on kit to give your Ogre scale figure the ram horned helmet (or just say the Highland cow Minotaur is a Ram)
-Pisces: Qoi, or two Qoi since I guess the symbol is two fish, but I feel like that makes Gemini less special…
-Aquarius: find a water jug from another line and have your favorite barbarians pouring it out
-Gemini: now here’s where it gets weird: are you literally looking for TWINS? Because the only canonical twins I can remember are the zombie chick beast master and the Giant Evil Knight. But they don’t look a thing a like anyone not in the cult who is 100% behind the lore would look you right in the eyes and say “they ain’t twins, you stupid idiot!”… if you want a Todd McFarlane take on concept the bone dog that comes with the Zombie Chick Beast Master has a double head adapter so you can make any figure a conjoined twin… but of course nothing is stopping you from just buying two of your favorite figure and saying “they’re twins”
