Thanks, alynnidalar and Dormouse559.
@Dormouse, yeah, mine too.
@alynnidalar, not necessarily that specific, depending on what you meant by "specific".
I'm thinking of "classificatory kinship systems",
those in which a man's brother's kin by any kinterm, are his own kin by that same kinterm,
and a woman's sister's kin by any kinterm, are her own kin by that same kinterm;
and reciprocally, anyone's male relative's brother, is kin to them by the same kinterm that relative is kin to them,
and anyone's female relative's sister, is kin to them by the same kinterm that relative is kin to them.
I'm going to follow this up by a post in some other ACH thread -- not this "quick question" thread, since it's not just going to be one question, and might not be quick.
I'm going to ask about fourth- and fifth- -degree relatives (probably among others); including, for instance, parent's sibling's spouse's sibling's children. I don't think the English term "cousin" actually covers these, at least not universally or not well; I don't think your parent's sibling's spouse's sibling counts as your "aunt" or "uncle" in English, at least not in all 'lects or not with uncontroversial grammaticality (if "grammaticality" is the right term).
That "parent's parent's sibling's child's spouse's sibling's spouse's parent's sibling's child's child" example --
-- an 11th-degree relationship which is twice affine, if I'm counting right and even correctly understand the meaning of "affine" --
-- is a very extreme example of things I'd like to know; I'm not confident I'll ever find out.
But thanks to everyone who answers!