Jocasta seems to intuite that the rumors about the abominable crime that is bringing devastation to Thebes are related to her incestuous marriage. Deep down, she fears that she has in fact married her own son. However, one part of her rejects the idea, and she does everything in her power to prevent Oedipus from believing in prophecies.
You may remember that Oedipus Rex begins when Oedipus and Jocasta have been happily married for twenty years and raised four children. In her desperate need to protect her family, Jocasta would rather turn a blind eye on the truth.
Oedipus, on the other hand, is ruled by his inner conviction that he did not murder his father but a stranger, and that Jocasta cannot be his mother. His hubris finally fulfills the curse laid on the royal house of Thebes by Pelops, king of Pisa. Oedipus summons the witnesses to his alleged death as an infant. The shepherd's confession that he did not abandon him in the wild but gave him to the royal couple of Corinth, added to Tiresias' reluctant confirmation of this and other ensuing deceptions, put the shocking truth together.
Therefore, Jocasta and Oedipus' relationship in the play is one of extreme tension. She places love and family above all other things and is ready to manipulate and discard whatever facts might destroy the status quo. He wants the truth at any cost, mainly because he feels so self-confident that he cannot envisage the consequences.