Chiron

The centaurs all had mothers who were clouds. This was a trick played on Ixion, their father, by Zeus. Ixion, a lowlife human, had killed his father-in-law and was shunned by all save Zeus, who invited him to Olympus for the weekend to tell him how he did it. Once there, Ixion got horny for Zeus's wife, so Zeus spiked his drink and made Ixion think a cloud was Hera. Next thing you know, Centaurus is born. (Clouds have a short gestation period.)

Centaurus grew up to have a thing for horses, so knocked up all the mares he could find. That's where all the centaurs came from. The centaurs begot the Visigoths who begot the Pagans and the Breed. They were a rowdy lot. They liked to hang out with the Satyrs, drink wine all day and worship Dionysus.

Not so Chiron. His father was Cronus, god of watches. His mother was a nymph. How those two begot a halfhorse / halfman is any one's guess, but beget they did.

Chiron grew up in a cave. He read the stars and found there the power to heal. He started a cult and inducted the likes of Jason and Achilles and Heracles to become disciples. Chiron played a mean lyre and fomented peace. As such, he became an enemy of the state.

Zeus hired Heracles to assassinate Chiron. Heracles, armed with a bow and arrows dipped in Hydra gall blood, got in a shootout with a herd of centaurs and got the better of them. Got the better of Chiron, too, right in the foot. Nothing is more toxic then Hydra gall, so it laid him down and smarted something awful.

Well, everyone had forgotten that Chiron was immortal. That meant he would have to spend eternity in agonizing pain. Meanwhile, Prometheus, who was at the time chained to a rock and getting his liver chewed out daily by an eagle because he had pissed Zeus off, was in considerable pain as well. A sort of hostage trade was worked out wherein Prometheus was freed (although he did have to lug around that damned rock wherever he went) and Chiron got to die. Makes no sense to us, but it"s justice to the gods.

In the end, Chiron got placed in the night sky as Centaurus. At the time, all the northern sky was taken, so he got stuck up in a distant corner of the southern sky. They say he's aiming his arrow at Aquila, Prometheus's liver-eating eagle, but I think it more likely he's planning a trick shot and the trajectory is toward that poseur Sagittarius. There's not room in the sky for two centaur archers.