Genesis 46:23 - John Gill's Exposition of the Entire Bible

And the sons of Dan, Hushim. He had but one son, wherefore the plural is put for the singular, see Genesis 46:7; Aben Ezra thinks he had two sons, and that one of them was dead, and therefore not mentioned; but the other way best accounts for the expression; though, as Schmidt observes, the plural may be indefinitely put, and the sense be this, as for the sons of Dan, there was only one, whose name was Hushim. Dan was a son of Jacob by Bilhah, Rachel's maid, as the following was another.