Charles Ellicott Commentary 1 Chronicles 2:21-24

"And afterward Hezron went in to the daughter of Machir the father of Gilead, whom he took [to wife] when he was threescore years old; and she bare him Segub. And Segub begat Jair, who had three and twenty cities in the land of Gilead. And Geshur and Aram took the towns of Jair from them, with Kenath, and the villages thereof, even threescore cities. All these were the sons of Machir the father of Gilead. And after that Hezron was dead in Caleb-ephrathah, then Abijah Hezron`s wife bare him Ashhur the father of Tekoa." — 1 Chronicles 2:21-24 (ASV)

This short section, concerning other Hezronites than those of the house of Caleb, is a parenthesis relating to a Hezronite element in Manassite Gilead.