In some versions of the Greek Oedipus myth, the source of Laius' curse—that his son will kill him and sleep with his wife—comes from an earlier sin. The stories vary in detail, but the main plot goes thus:
Laius was the son of Labdacus, the king of Thebes. Labdacus passed away while Laius was still young, and regency was given to the evil Lycus. Lycus was soon overthrown, however, by the twins Amphion and Zethus. To save his life, Laius was sent to Pelops, the ruler of Pisa, a kingdom near Olympia. Laius was welcomed there, but as he grew up he was consumed with lust for Chrysippus (Chrysippe), the illegitimate son of King Pelops. Because of this, some say that Laius invented homosexual pederasty, or homosexuality itself.
When Amphion and Zethus died, Laius was free to return to Thebes as its rightful ruler. He kidnapped Chrysippus and took him back to Thebes, where he raped him and made him his unwilling lover. The stories vary here—Chyrsippus either died as a result of the brutal rape, killed himself in shame, was killed by Laius, or was rescued by his father.
Later, when he was married to Jocasta, Laius found that the couple could not have children. He consulted the Oracle at Delphi, and was told his curse, the punishment for his sin: his son would kill him and have children by his mother. He vowed never to have children. Drunk one night and lusting for Chrysippus, he impregnated Jocasta. Their son was the famous Oedipus.
Chrysippus was also the name of an influential Stoic philosopher. But I don't know a thing about him.
liveforever says re chrysippus: Hmm. No, the curse on the royal family of Thebes goes even further back than that. It plagued the family since their ancestor Cadmus incurred it, by slaying Ares' pet dragon (to found Thebes).
I will do some more research. Some of what I read mentioned that the curse was the result of the rape, but this may be false, or the accounts simply may vary.