Divrey Hayamim Bais 21:4

4 Now when Yehoram was risen up to the Mamlachah of his av, he strengthened himself, and slaughtered all his achim with the cherev, and also a number of the sarim (leading political figures) of Yisroel.

Divrey Hayamim Bais 21:4 Meaning and Commentary

2 Chronicles 21:4

Now when Jehoram was risen up to the kingdom of his father,
&c.] Succeeded him in it, and reigned alone, for he had reigned with his father some years before his death; (See Gill on 2 Kings 8:16), he strengthened himself;
in the kingdom, by some means or another closely attaching the greater part of the princes, and people of the land, unto him, when he thought himself well settled and established on the throne; though some understand it of making strong, or hardening his heart to do what is next mentioned: and slew all his brethren with the sword;
either to get their riches into his hands, or lest, being religious princes, they should oppose his restoring idolatry, and for that reason the people should depose him, and set up one of them; and therefore he dispatched them out of the way to secure himself, and carry his point: and [divers] also of the princes of Israel;
such who had removed out of the ten tribes, for the sake of religion, and therefore would never agree to the introduction of idolatry among them, for which reason Jehoram slew them; and perhaps they might express their disapprobation and abhorrence of his murder of his brethren.

Divrey Hayamim Bais 21:4 In-Context

2 And he had achim, the Bnei Yehoshaphat, Azaryah, and Yechiel, and Zecharyahu, and Azaryahu, and Michael, and Shephatyahu. All these were the Bnei Yehoshaphat Melech Yisroel.

3 And their av have given them mattanot rabbot of kesef, and of zahav, and of precious things, with fortified cities in Yehudah, but the Mamlachah (Kingdom) he gave to Yehoram; because he was the bechor.

4 Now when Yehoram was risen up to the Mamlachah of his av, he strengthened himself, and slaughtered all his achim with the cherev, and also a number of the sarim (leading political figures) of Yisroel.

5 Yehoram was thirty and two years old when he began to reign, and he reigned shemoneh shanim in Yerushalayim.

6 And he walked in the derech of the melachim of Yisroel, as did the Bais Ach’av, for he had the Bat Ach’av to wife, and he wrought that which was rah in the eyes of Hashem.