Laius

All he must do is find the murderer of Laius, the former king whom he replaced both on the throne and in Queen Jocasta’s bed.

King Laius of Thebes was the third in descent from Cadmus.

Jocasta tries to reassure her husband that oracles don’t always get it right by telling him that one once told Laius that he would die by his son’s end.

Or consider the sentence from the Wikipedia entry on Oedipus: The baby, he says, was given to him by another shepherd from the Laius household, who had been told to get rid of the child.

Understandably, his father, Laius — king of Thebes — wasn’t particularly keen on the idea, so he left baby Oedipus on a mountain to die.