>>So the aunts' husbands were related to the patriarch via female members of the family, and ranked so much lower that they didn't deserve distinct names. They basically married _into_ the family, so they were pretty much outsiders.
>
>So the distinction is only relevant where you have that kind of a hierarchy, which is presumably why you don't have the distinction in English and the Romance languages.

Exactly. Some of that has already vanished from the memory - I don't distinguish jetrva from zaova (one should be brother's wife, the other would be husband's brother's wife or vice versa) while my parents still know exactly which is which. Some of it has gone even from the language; there are words for some obscure relations that nobody really knows what they mean, except maybe ethnologists.