The best and meetest — i.e., the one you think best qualified in every sense (not merely in the moral sense).
Your master’s sons. — “Your master” need not mean Jehoram. The story relates to Ahab (2 Kings 10:1).
His father’s throne — i.e., Ahab’s throne. (Comp. 2 Chronicles 17:3; 2 Chronicles 21:12; 2 Chronicles 29:2, where David is called the father of Jehoshaphat, Jehoram, and Hezekiah in turn.)
Fight for your master’s house. — Jehu thus declares his own warlike intentions, leaving the nobles, whom his prompt and decisive action had taken by surprise, no choice between improvised resistance and instant submission. Knowing Jehu’s character as a soldier, they chose the latter.