Oedipus and Adoption
Oedipus was the son of King Laius of Thebes and Queen Jocasta. There was a prophecy that Laius would be killed by his own son, so the baby was abandoned on a mountainside to die. (This was a common practice in ancient times for unwanted children: Hansel and Gretel and Snow White are fairy-tale examples. Compare the entries for feral children, foundlings and Nebuchadnezzar.)
He was found by a shepherd and given to King Polybus of Corinth, who adopted him, pretending he was his own child. When he grew up he was told in a prophecy that he would kill his father and marry his mother; to avoid such a terrible fate he left home and the people he thought were his parents to wander the world. On his travels he met and accidentally killed Laius. Later he arrived at Thebes, where he rid the city of the monster Sphinx. His reward was the hand of the widowed queen - Jocasta. They had children, but eventually it was revealed what their real relationship was and that the man he had killed was his own father. In horror Jocasta killed herself, while Oedipus blinded himself and went into exile.
The story is the basis of one of the most famous play cycles of ancient Greece, by Sophocles.
Microsoft Encarta 98 Encyclopedia, 1993-97 Oxford Classical Dictionary, edited by M. Cary, et al. (Oxford: Oxford University Press, 1949) "Oedipus the King" [The myth]. Available at:  Sophocles. "Oedipus the King" [The first play in the cycle]. Available at:  Brinich, Paul M. "Psychoanalytic Perspectives on Adoption and Ambivalence." Available at: