Ahithophel in Wikipedia

("Brother of Insipidity", or "Impiety") was a counselor of King David and a man greatly renowned for his sagacity. At the time of Absalom's revolt he deserted David (Psalm. 41:9; 55:12-14) and espoused the cause of Absalom (2 Samuel 15:12). David sent his old friend Hushai back to Absalom, in order that he might counteract the counsel of Ahitophel (2 Sam. 15:31-37). Ahitophel, seeing that his good advice against David had not been followed due to Hushai's influence, correctly predicted that the revolt would fail. He then left the camp of Absalom at once. He returned to Giloh, his native place, and after arranging his worldly affairs, hanged himself, and was buried in the sepulcher of his fathers (2 Sam. 17:1-23). It would seem from a conjunction of II Sam, 23:34, and 11:3, that Ahitophel was the grandfather of Bathsheba, and it has been suggested, as an explanation of his conduct towards David, that he had kept a secret grudge against the King for the way he had treated Bathsheba, and her first husband, Urias. This, or some motive of ambition, would be in keeping with the haughty character of Ahitophel...