Their sisters were Zeruiah and Abigail. The three sons of Zeruiah were Abishai, Joab, and Asahel.
Notes from Wikiquote
1 Chronicles 2:16-17 NCB.
Quote text and notes from Wikiquote: Amasa (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.