Well, it's based on a translation of an Italian novella, so there's that. The Montagues were a real family. There were lots of families that had violent rivalries in the cities of northern Italy (but not so much Venice). All that being said, I'm not sure how many elements of the story are distinctive of any society (besides the fractious families, but you can find that in a lot of places, perhaps to to the same extent as Italy), which is what makes the tale and others by Shakespeare so adaptable.