One of my friends keeps calling the son of the sister of her husband her "husband's nephew".
This is correct but it seems rude to me. It sounds like she is trying to put some distance between her and that teenage boy. She is Korean and in Korea has lots of words to describe the exact relation between people, so I guess she does it by habits. She s actually quite fond of the boy and they meet regularly.
It sounds wrong to me. If the husband of my aunt (my mother's sister) was speaking about me as "his wife's nephew", instead of "my nephew", I would feel offended. I am French so not a native English speaker but I believe we have the same cultural norms on that point.
Is calling your husband's nephew that way, instead of "my nephew", considered as rude ?
Note: this happens in casual situations, not when blood relations would actually matter (genetics, inheritance,...)