Andor was modeled on Great Britain and the Two Rivers on it's bucolic shepherding, peasant villages, right? So since when did isolated farmers and shepherds, or European royalty for that matter, have any compunction around marrying their cousins?
Yeah, true, Lord knows they were free with that sorta thing.
For one, modeled after=/=is. It is hardly the only difference. For another, I think he was worried that they were very closely related.
I'd agree with this, if it weren't for one simple thing; the Congar's and Coplin's in the TR. I'm not looking it up, mostly cause I'm lazy, but also because it's late, but I'm pretty sure it's stated early in EotW that they're super inter-married. Surely, at least first-cousins are married somewhere in there; wouldn't surprise me in the least if step or half-siblings were as well.