What does 2 Chronicles 21:13 mean?

'You've led Judah and Jerusalem into the same kind of unfaithfulness as Ahab's family did in Israel. You've even killed your own brothers, men better than you.' 2 Chronicles 21:13 - Modern Text Bible

(The letter accuses Jehoram of corrupting his people and murdering his brothers, who are described as more righteous than he is.)