In the play "Oedipus the King" by Sophocles, Oedipus causes suffering to his family and the kingdom by his actions and his ignorance of the truth.
Oedipus was the son of King Laius and Queen Jocasta of Thebes. When Oedipus was a baby, a prophecy was made that he would one day kill his father and marry his mother. In an attempt to avoid this fate, Laius abandoned Oedipus on a mountainside, but Oedipus was rescued and raised by another family. When Oedipus became an adult, he learned of the prophecy and left his adoptive family to avoid fulfilling it.
However, as he traveled, Oedipus encountered Laius on the road and, not knowing who he was, killed him in a fit of anger. Oedipus then came to Thebes, where he solved the riddle of the Sphinx and was made the city's king. He married Jocasta, not knowing that she was his mother.
As Oedipus's reign progressed, a plague struck Thebes and the city was in crisis. Oedipus, determined to find out the cause of the plague, sent his brother-in-law, Creon, to consult the Oracle at Delphi. When Creon returned with the news that the plague was a result of Laius's murder and that the killer was still at large in Thebes, Oedipus vowed to find and punish the murderer.
As Oedipus's investigation continued, he eventually learned the truth about his past and that he had unknowingly fulfilled the prophecy. When he realized that he had killed his father and married his mother, Oedipus was devastated and blinded himself in grief and guilt. His actions had caused suffering to his family, as his wife/mother Jocasta hanged herself upon learning the truth, and to the kingdom of Thebes, as the plague continued to ravage the city.