We are not told very much about the state of Oedipus and Jocasta's marriage before the play begins, culminating in tragic revelations for both people. However, we are give a few clues telling us that Oedipus treated Jocasta with the utmost kindness and respect and that the couple did have a happy marriage.
We first learn of Oedipus's respect for his wife when Creon responds to his accusations of treason. As part of his argument, Creon points out that Oedipus has granted Jocasta equal rule over the city and even shares ruling the city with himself as well, as we see in Creon's line, "Do you grant equal rule of this land to her [Jocasta]?" (605). Oedipus even confirms his respect for his wife and the kindness he treats her with in his following line, "All that she desires she has from me" (606). We also learn of the respect in which Oedipus treats his wife with when she comes to break up the fight between Creon and Oedipus. Oedipus respects his wife's opinion so much that he allows himself to be pacified, allows Creon to go home, and allows Jocasta to convince him that Creon is faithful.
Later, we learn from the chorus that their marriage was indeed a happy one. After Jocasta hangs herself and Oedipus stabs out his eyes, the chorus laments that so much tragedy and agony has befallen what was such a happy couple, as we see in their lines:
Their old happiness that was before was justly called happiness, but now on this one day mourning, madness, death, disgrace ... none have been absent. (1312-15)
Since the chorus states that they truly were a happy couple, we know that prior to the beginning of the play, the couple had a very strong and happy marriage that was full of mutual respect and kindness.