The families of the Levites are here numbered by themselves, because they were not to have a distinct share of the land, whence it is that they are not so distinctly and exactly mentioned as the other tribes, but confusedly and imperfectly, some of them being wholly omitted here. See Exodus 6:17-19.
Related Commentaries of Numbers 26:58
Numbers 26:58
58 These are the families of the Levites: the family of the Libnites, the family of the Hebronites, the family of the Mahlites, the family of the Mushites, the family of the Korathites. And Kohath begat Amram.