AIBU to be upset by this or is this a "nothing" thing?

[RunnerBum]

I met my DH 12 years ago, married for 7 and a half years - 2DCs. My DSis and BIL originally met around the same time I met DH but broke up about four years later for about three years. They got back together, and recently got married and have a DC. All four of us get on well. My DSis has previously (but not recently) expressed concern that I got married so young (early 20s) but not sure if this plays any part. We have 2 DBros - one has been on-and-off with his GF for 6 years but are now expecting a baby, the other has been with his fiancée for one year (no children). DSis and I are the closest of the four of us largely because we live much closer - one DBro has never met any DCs or DN, the other has met my DC1 3 times and my DC2 and DN just once. But there are plenty of messages/phone calls/video calls etc.

My DCs call all my siblings and their partners auntie/uncle except for DBro's fiancée (because they haven't been together long) but we're starting to integrate that now that they're engaged and my youngest (who isn't speaking yet) will know her as Auntie.

My DSis calls everyone DN's auntie/uncle except for my DH. I find it a bit odd, as if it may be an intentional choice to exclude him. DH hasn't mentioned anything but he's very close to DN - we were really struggling with secondary infertility when DN was born and DH spent a lot of time cuddling and playing with him as a result.

Should I raise or let it go? I've been signing things from us as auntie and uncle - should I stop using it too?

Just ask!?

If you think you can't ask because she'll react badly to criticism, you could maybe drop "uncle" from BIL's name and see if she raises it, then say you've noticed she doesn't refer to H as uncle so you were following that lead.

Though I did think there might be something like PPs have said that she knew DH well before he was an uncle so she's got a bit of a mental block with it. My sister and I were good friends with the girls of another family. My mum was very formal about manners and insisted we call the mum Mrs Jones. After a couple of years the mum said this is silly, please call me Jane or Auntie Jane if that is more comfortable. But we just couldn't do it! We tried to honour her wish but it kind of got stuck before it left my mouth and is end up saying Mrs Jones!

What do YOU think the reason is? Does she give the impression in other ways that she considers he isn't really part of the family? My MIL for example used to introduce her daughter's partner as exactly that, but me as "our son's friend".

I’d guess it’s because your DH has been around the longest and predates the whole auntie uncle thing.