1 Kings 22:51

By comparing this verse with 1 Kings 22:41, it appears that Ahaziah was made king by his father, and reigned in conjunction with him, a year or two before Ahab's death, and as long after it; even as Jehoram the son of Jehoshaphat was made king by his father in his lifetime, as we shall see hereafter; which possibly was done in compliance with Ahab's desire upon marriage of his daughter to Jehoshaphat's son; and it may be Ahab, to induce and encourage him to do so, gave him an example of it, and made his son his partner in the kingdom. Reigned two years; either after his father's death; or one before it, and another after it.