John Gill Commentary Genesis 46:23

"And the sons of Dan: Hushim." — Genesis 46:23 (ASV)

And the sons of Dan, Hushim .
] He had but one son, therefore the plural is put for the singular, see (Genesis 46:7Genesis 46:15) ; 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.