So there's a thread in General Discussion asking for the ability to change last names after completing the marriage quest, but it got me thinking... do the five races of Eorzea actually practice that custom? I started trying to guess through it for each race and I realize now it got a little out of hand and is longer than I meant it to be and I'd love some input! What do you guys think?
It's very unlikely either clan of Lalafell do, since both names for them are actually given names, and they're rarely even addressed by their "first" name alone. It'd be like "Jessica" marrying "Daniel" and changing her name to "Jessiel."
It's equally unlikely the Seekers of the Sun practice such a custom, mostly since they don't have anything resembling marriage in their society.
We have very little information on Keepers of the Moon relationships, so I don't have a guess either way with them.
While Sea Wolves MIGHT, the emphasis is obviously on parentage, since their last names are just <so-and-so's son/daughter>. In Iceland this is still practiced in full, with somebody named... Arianna Jonsdottir, for example, actually being the daughter of Jon. If she marries Rurik Einarsson she does NOT become Arianna Einarsson. So it's unlikely Sea Wolves do it.
The Hellsguard seem more like the Lalafell in that both parts of their name are equally relevant to their identity, and are thus equally unlikely to do it.
Since the Elezen follow French conventions I see no reason why they wouldn't -- provided there's no cross-clan marriage, I imagine that would be fairly taboo for them.
I feel it's unlikely Midlanders do since their names are based on their (not their father's) professions or can reflect their appearance. This implies that, while their names can change throughout their life, it more reflects an individual than an individual's spouse.
Highlanders don't seem overly likely to since they tend to adopt the nicknames they've earned in battle, implying they earn their names (though maybe not completely, I guess they might take married names).
TL;DR: Probably not for pretty much every race but the Elezen and maybe the Keeper Miqo'te.