My postdoc advisor is almost never in the office: between living far from the university and traveling frequently (which yields the research funds that support all of us), it's just not practical for him to come in more than a few times a month. I never got introduced to anyone, so only met the people immediately around me. At the holiday party, I met everyone else, which was overwhelming.
Meeting them all at once, I noticed something: the group at the party was almost entirely female (unusual) and absolutely everyone was married, even the graduate students. I didn't go around asking who was married or looking at ring fingers, but most volunteered it. By contrast, maybe 1/4 of graduate students where I came from were married, and maybe a bit over 1/2 by the time we all finished.
The university itself is pretty average overall, and this part of it looks like it's where the wives of people who have other reasons to be here tend to go. When one member of a dual career couple gets a top-notch offer, the other has to take whatever jobs are in the area, which are usually less prestigious, but it was interesting that in this case, such a large proportion of the people here were in the same position. Perhaps it's not surprising: the university is not top-notch, but this particular research group has funding as good and prestigious as better universities.