Gadol, Gez refers to “original” Lubavitch families from Russia, as opposed to other groups who became Lubavitch, BTs and gerim. As far as I’ve heard, there’s a strict hierarchy where non-gez people cannot marry gez families. BTs and gerim usually are in the same boat too. Whereas in the rest of the Torah world, this isn’t so; it’s not always a meritocracy, but it’s much closer to one.
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