Abigail is one of David's two sisters. The other sister is Zeruiah, who is the mother of Joab, famous as David's commander, Abishai, and Asahel.
1 Chr 2:13Jesse was the father of Eliab his firstborn; the second, Abinadab; the third, Shimea;1 Chr 2:14the fourth, Nethanel; the fifth, Raddai;1 Chr 2:15the sixth, Ozem; the seventh, David.1 Chr 2:16Their sisters were Zeruiah and Abigail. The sons of Zeruiah were Abishai, Joab and Asahel, three.1 Chr 2:17Abigail bore Amasa, and the father of Amasa was Ishmaelite Jether.