2 Samuel 17:25

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.

Amasa. By the genealogy it appears that this captain stood in the same relation to David as Joab, both being his nephews. He seems to have been an illegitimate son, his father, Ithra, being an Israelite, and his mother an Ammonitess (see the notes at 1 Chronicles 2:16), and of course Amasa was Absalom's cousin.