What does 2 Samuel 3:5 mean?

Sons were born to David in Hebron. His firstborn was Amnon, of Ahinoam the Jezreelitess;

and his second, Chileab, of Abigail the wife of Nabal the Carmelite; and the third, Absalom the son of Maacah the daughter of Talmai king of Geshur;

and the fourth, Adonijah the son of Haggith; and the fifth, Shephatiah the son of Abital;

While there was war between Saul’s house and David’s house, Abner made himself strong in Saul’s house.

Now Saul had a concubine, whose name was Rizpah, the daughter of Aiah; and Ishbosheth said to Abner, “Why have you gone in to my father’s concubine?”

Then Abner was very angry about Ishbosheth’s words, and said, “Am I a dog’s head that belongs to Judah? Today I show kindness to Saul’s house your father, to his brothers, and to his friends, and have not delivered you into the hand of David; and yet you charge me today with a fault concerning this woman!