John Gill Commentary 2 Kings 8:25

"In the twelfth year of Joram the son of Ahab king of Israel did Ahaziah the son of Jehoram king of Judah begin to reign." — 2 Kings 8:25 (ASV)

In the twelfth year of Joram the son of Ahab, king of Israel
did Ahaziah the son of Jehoram king of Judah begin to reign .
He is called Jehoahaz, and said to be the youngest son of Jehoram, (2 Chronicles 21:17) .