Biron / Comet / "Bronco Bill"

Earth-One
Later, the two went on a mission with her to the planet Zerox, where a magic spell was cast that turned him into a human, but only while a comet passes through the solar system he is in. As a human, he adopted the identity of "Bronco" Bill Starr, a rodeo trick-rider, He would occasionally romance Supergirl, who was totally unaware he was actually her pet horse!
 * 1)  Kara Zor-El / Supergirl  - Biron was originally an ancient Greek centaur. The witch Circe gave him a potion to turn him fully human, but by the machinations of the same enemy, she mistakenly made him fully horse instead. To make up for this, Circe gave him super-strength, telepathy and immortality. His enemy later imprisoned him in an asteroid.. When Supergirl's rocket passed, it broke the force field, enabling him to escape. He became Supegirl's pet horse, dubbed Comet the superhorse, with her totally unknowing he was a sentient being.

2.  Lois Lane  - Yep, he romanced Lois Lane multiple times as well!