Charles Ellicott Commentary 1 Chronicles 10:6

"So Saul died, and his three sons; and all his house died together." — 1 Chronicles 10:6 (ASV)

And all his house died together. —Instead of this, Samuel reads, and his armour-bearer; also all his men on that day together. The Septuagint adds on that day here, while in Samuel it omits all his men, thus minimizing the differences of text. It is mere pedantry to press the phrases all his men, all his house. The strength of these expressions indicates the completeness of the overthrow.

The chronicler was fully aware that some of Saul’s house were not engaged in this battle (1 Chronicles 9:35). And in any case, the chief warriors of his household, and immediate followers, died with the king.