After some thinking I came across some more examples in a bit different context.

There are also expressions like "взять/брать в жёны/мужья".
A взяла в мужья Б. - A is a woman, and she married B (she's "taken him in husbands").
C взял в жёны D. - C is a man, and he married D (he's "taken her in wives").

Another expression is "напрашиваться в друзья" - to force one's friendship upon somebody: Он напросился ко мне в друзья. - He forced my friendship upon himself. (Literally: He forced himself to my friends).

But the base meaning is still the same: "to join a specific group, to become one of them".