Albert Barnes Commentary 1 Chronicles 6:28

"And the sons of Samuel: the first-born [Joel], and the second Abijah." — 1 Chronicles 6:28 (ASV)

Vashni - The true name of Samuel’s firstborn, which was “Joel” (see the margin and references), has been omitted here, and the word that properly means “and his second son” has been mistaken for the name of the first.