Clansmen

Common wisdom says you talk about unity at this time of the year. After all, tonight we segue from the sobriety of the Three Weeks to the somberness of the Nine Days, with the advent of the month of Av, when the Temple was destroyed, we are told, due to baseless hatred (Yoma 9b). So it's customary to denounce division at this time -- even though that's exactly what this week's Torah reading talks about (Num 33:53-55):

Take possession of the land, and live in it, because I have given you the land to inherit. You are to divide by lot the land among yourselves, by your clans. The larger the clans are in number, the larger their inheritance is to be. The fewer the clans are in number, the lesser their inheritance is to be. To whomever the lot falls, that inheritance goes to him. Divide it according to your ancestral tribes.

The Jewish nation is split up genealogically -- into tribes, then clans, then (ancestral) houses--much as the US is split into states, counties and localities. "By your clans" is one word in the original Hebrew, lemishpechoteikhem. If you can pry apart that hexasyllable, you might recognize mishpacha, often translated family. But these "families" were massive, with an average population of well over ten thousand adult males, so the term "clan" is probably more accurate.
It's notable that we find this precise term in only one other place: when Moses gives the first mitzva to the Jewish people in Egypt (Exodus 12:21):

Then Moses summoned all the elders of Israel and told them, “Choose sheep for your families, and slaughter the Passover lamb."

Even before the Exodus, in the ghetto of Goshen, the Jewish people must organize themselves by clans and ancestral houses (ibid. v. 3), in order to prepare for their destiny in the Promised Land.
In fact, this is a theme running through the entirety of the Book of Numbers. In all the other four books of the Torah, mishpacha shows up a total of 26 times; in Numbers, 159. The specific conjugation lemishpechotav (by his clans) shows up twice.

So the Israelites did everything just as the LORD had commanded Moses; that is, they encamped and traveled under their banners, each man by his clans, upon his ancestral house. (2:34)
Moses heard the people weeping by his clans, each man at the entrance of his tent; the LORD was very angry and it was bad in Moses' eyes. (11:10)

The Jews divide themselves by tribe, clan and house at the foot of Mt. Sinai; but once they start traveling, literally at the first encampment, they start crying. The proximate cause is the food, but the Midrash (Sifre ad loc.) seeks a deeper reason, declaring that it was mishpacha matters which perturbed them. Now, the Midrash takes mishpacha to mean close family in this context, explaining that the people were bummed they couldn't shtupp their sisters-in-law anymore.
However, as we have noted, that's not really what the word denotes in Numbers. It seems that they were bothered by the clannishness. Before Moses showed up, they were simply Hebrews, set apart by their national identity, dress, language, etc. They were slaves, but they were a unified people. With the Book of Numbers, that changes:

And they called the whole community together on the first day of the second month. The people registered their ancestry by their clans and ancestral houses, and the men twenty years old or more were listed by name, one by one. (1:18)

Unity is easy in exile and under oppression. To be "the whole community" in the ghetto is simple enough, even if life itself is anything but. Coming into the Promised Land, going from minority to majority status, presents a new challenge. Suddenly clans and tribes and houses make a difference, and it's enough to make one weep. Can we build a society based on our commonalities, while celebrating our differences? Well, third time's a charm. Let's get to work.