Albert Barnes Commentary 1 Chronicles 8:1

"And Benjamin begat Bela his first-born, Ashbel the second, and Aharah the third," — 1 Chronicles 8:1 (ASV)

The reason for this return to the genealogy of the Benjamites seems to be the desire to connect the genealogical introduction with the historical body of the work. As the history is to begin with Saul, the genealogical portion concludes with an account of the family of this Benjamite monarch.