Albert Barnes Commentary 1 Chronicles 8:40

"And the sons of Ulam were mighty men of valor, archers, and had many sons, and sons` sons, a hundred and fifty. All these were of the sons of Benjamin." — 1 Chronicles 8:40 (ASV)

Sons and grandsons - Based on the number of generations, this genealogy of Saul's house likely dates to the time of Hezekiah (Compare to 1 Chronicles 4:41). Ulam’s grandsons are in the thirteenth generation from Jonathan, just as Hezekiah is in the thirteenth generation from David.