New Defender's Study Bible Notes
1:17 Jehoram reigned. Note two Jehorams mentioned in this verse. The first is King of Israel, son of Ahab and brother of Azakiah (II Kings 3:1). The second was co-regent of Judah with Jehoshaphat his father.
1:17 second year of Jehoram. Jehoram had apparently been installed as co-regent over Judah with Jehoshaphat his father just two years before another Jehoram, younger son of Israel’s king Ahab, began his own reign. This was the eighteenth year of Jehoshaphat’s reign (II Kings 3:1). It was fairly common during that period for kings to appoint sons as co-regents, in order to forestall later disputes that might develop when the reigning monarch died.