[quote=TheSovereignGrave]
I don't think the culture is really that big of a deal. I mean, the Hanarth have names like Napizzi, Uthros, Elotian, Suthra, etc. while both Frisstreek and Marmon people use names like Russell, Henri, Henry, Gregory, and Sara. And it's not like there's a sort of unifying factors among the myriad societies.
[/quote]

Names generally aren't the sole thing in a culture, and pretty fairly over-simplifies the concept.

Though it is possible for two to not "match". But in these events one or the other are not as local to the area. Or they need to inhabit two completely different biomes and have some very major geographic division between them that would have limited cultural exchange or forced exchange to become ultimately irrelevant. Other factors might boil down to how readily one's agricultural practices may translate to someone else's (which is a long and complex Guns, Germs, and Steel thing). But you'd be looking at the differences between Incan and Amazonian tribes in comparison to the Aztec and Mayan, or pre-Islamic Iranians to pre-Islamic Turks.

Hungarian culture and language is a fairly big example of how one can differ from their neighbors. The Hungarians are in actuality not Slavic, they're more closely related to Finnish than they are the Russians and the Poles and originate from the edge of Siberia. Through tribal migration and invasion they came to fill in the underpopulated Carpathian Basin and ultimately divided the settled Slavic tribes between South and East Slavs.