Why does the Torah use the plural "u'Vnei" with regard to Dan, who only had one son?
Ramban (to 46:7): It is the way of the Torah to sometimes do this. 1
Targum Yonasan: Chushim is not the name of Dan's son. The Pasuk means that the sons of Dan were zealous and merchants, and were innumerable. 2
Ibn Ezra: There were two sons, and one of them died. 3
Tosfos ha'Shalem (6, citing R. Yehudah ha'Chasid): Dan also had a son Shucham, who had only daughters. They married Chushim's sons, so the entire Shevet is called by Chushim's name. 4
Malbim (Bamidbar 26:8, Divrei ha'Yamim I, 2:8): The plural always teaches more than one; sometimes there is a reason to list only one. Later, Dan had other sons; here we list only those who descended to Egypt. "U'Vnei Falu Eli'av" - Falu had other sons; some say that he is Peles, Ohn's father. Only Eli'av is listed, for the next verse teaches that Dasan was his son.
Though it is not clear why the Torah does not list them by name. See also Ba'al ha'Turim (citing Bava Basra 143b). Targum Yonasan also presents details concerning the sons of Yisachar and Zevulun (apart of listing their names), as well as of Serach, Asenas (Yosef's wife), and the reason behind the names of each of Binyamin's sons - even though there is no indication for any of these in the Pasuk.
Moshav Zekenim rejects this. Also other verses use the plural for one - "u'Vnei Falu Eli'av" (Bamidbar 26:8), "u'Vnei Eisan Azaryah" (Divrei ha'Yamim I 2:8).
In Bamidbar (26:42), the only son of Dan listed is Shucham! This requires investigation. (PF)
What is the meaning of the name "Chushim"?
Targum Yonasan: Refer to 46:23:1:2.
Maharal (Chidushei Agados Vol. 3, p. 128, to Bava Basra 143b): The tribe of Dan multiplied like reed stalks 1 - i.e. all at once. Dan had only one son at the time of their descent to Egypt, yet after leaving Mitzrayim they were one of the largest tribes (see Bamidbar 1:38-39)! This is because the trait of Dan is Din, 2 which brings about rapid increase.
