Oedipus is a mythical or fictional king in Greek mythology. He is adopted as a baby. Without knowing who they are, he marries his biological mother and kills his biological father. The psychologist Sigmund Freud had a theory and he called it the Oedipus complex, after this story.
Oedipus has 4 children, Antigone, Polynices, Ismene and Eteocles. All of these are by his mother Jocasta. Later, they find out they are related to each other. Jocasta hangs herself and Oedipus rips out his eyes in disgust.