Absalom made Amasa captain of the host Amasa was another of David's nephews, the son of his sister Abigail. The daughter of Nahash Nahash was one of Jesse's wives, by whom he had this Abigail, the mother of Amasa, as he had Zeruiah, the mother of Joab, by another wife; so that they were sisters by the father, but not by the mother, and Joab and Amasa were cousins.
Related Commentaries of 2 Samuel 17:25
2 Samuel 17:25
25 And Absalom made Amasa captain of the host instead of Joab: which Amasa was a man's son, whose name was Ithra an Israelite, that went in to Abigail the daughter of Nahash, sister to Zeruiah Joab's mother.