Misunderstandings abound in Oedipus Rex.
First, when Oedipus hears of the prophecy that he would kill his father and marry his mother, he leaves home to avoid his fate. All seems well to him. However, there is a fatal misunderstanding. What he considers home is not really his home. And whom he think are his parents are not really his parents.
Second, on his way to Thebes, he kills a man for almost running him off the road. Oedipus thinks that this man is a stranger, but here again there is misunderstanding, as this man is his father. He, then, marry a woman in Thebes, but she is his mother. Another misunderstanding.
The people in Thebes, therefore, do not know who Oedipus really is. His family is filled with misunderstanding as well. Think about it, his daughters are his sisters and his sisters are his daughters!
Clarity comes to him through a blind seer. Ironic.