Cupid his himself on the head what was he thinking, this is Superman, the greatest hero in the world and of course he deserves more than one woman. Imagine what could happen if Superman the Earth because his girlfriend ditched him or his girlfriend died,
the Eath would die and Cupid loved the Earth, so much fucking.
Now the key question was who to put in the harem for Superman. Cupid had a lot of choices, he could make a super strong harem, a magic one, one with regular women or even one made of villainess.