I think this is a kind of funny myth. Ixion, the King of Lapiths (a really, really, really old city in Thessaly) fell in love with a girl named Dia. To get her, he promised this really valuable present as a bride price. Now, when it came time to pay, for whatever reason, Ixion doesn't pay. That's not the funny part.
Well, the father-in-law, not being the better man in this, decides to steal his horses. This makes the holidays really uncomfortable for all involved and relationships just go to Hades in a hand basket. Ixion, however, tired of all the conflict decides to invite his father-in-law to a dinner. No, he doesn't pull a Tantalus and feed him mystery meat. He instead lures the guy to fire area and pushes him onto a bed of hot coals and watches him burn to death. That is not the funny part.
The funny part is that Ixion is NOT punished by Zeus for this. In fact, Zeus feels pretty bad for the guy since everyone back on earth was treating him like he did something wrong (I mean, come on - it was only an in-law, right?). He lets him hang out in Olympus for a while.
To get a few more chuckles out of this, what does Ixion do to repay Zeus? He starts hitting on ol' ox-eyes herself. Hera. Of all the goddesses, he chooses the big man's main squeeze.
Zeus, suspicious of this, creates a cloud with a remarkable resemblance to Hera. He called the cloud Nephele (really creative name, it means "cloud"). Ixion puts his move on the Hera cloud and gets it pregnant (don't ask me how - can you imagine how complex sex ed must have been for a poor Greek lad living in myth times?)! Well, Centauros was the result and from him we get most centaurs.
Now, killing your father-in-law gets rewarded. Hitting on a cloud in the shape of Hera, that gets your butt fried by a thunderbolt. That and you get expelled from Olympus. And you get strapped to a wheel that is on fire and constantly spinning. I wonder if on his wheel if he gets to tell Tantalus, "Oh, you think you have it bad. What I would give to just be a little hungry!"
Morale of today's post: Kill your in-laws. Stay away from sexy clouds.