My sister's fiance has always been Uncle to Liebs. Well, since we knew he was a long-term boyfriend - Liebs didn't meet him much before that though. My cousins are aunties and uncles, their partners (now spouses in many cases) are aunties and uncles too. We're family! All my cousins' children are called DS's cousins. (Some of my cousins do this too, others don't: the ones that don't have siblings with children though!)

My husband's brother's children are his niece and nephew. Niece is being shaped up to be a right madam and Nephew is very "naughty" but only from lack of attention. I do not get to see them often, despite requesting it, and cannot change the people they are set to become if this treatment continues and I don't like that. I don't want to be associated with their upbringing. That's really mean. I don't disown them to their faces or to those who know me IRL, but just to DH and on here I usually call them his niece and nephew.