Abigail

Avshalom had put 'Amasa in charge of the army in place of Yo'av. 'Amasa was the son of a man whose name was Yitra the Isra'eli, who had had sexual relations with Avigal the daughter of Nachash, Tz'ruyah's sister and Yo'av's mother.

and their sisters Tz'ruyah and Avigayil. The sons of Tz'ruyah: Avshai, Yo'av and 'Asah'el, three of them.

Avigayil was the mother of 'Amasa; the father of 'Amasa was Yeter the Yishma'eli.