I'll preface this by saying I know on MN adults celebrating birthdays is frowned upon, but here goes!
I celebrated a big birthday a couple of weeks ago. When first talking about ideas with my DB, I'd mentioned that I was keen my niece and nephew could come (they are primary age) and so came up with a plan of going to a daytime BBQ event. Its somewhere I would have been happy to go to anyway, but choosing that for my celebrations and it being an afternoon was definitely to make it suitable for them. There aren't any other young children in the family and DH and I don't have children. We'd talked a few times since about it to make sure it was suitable eg the food choices, play area, what time of day etc.
DB messages me quite last minute to say that he's not well so can't make the event. Bit disappointed but these things happen. He didn't mention SIL and the children but assumed that either they were unwell or SIL had her hands full if he was ill.
Through chatting to another family member since then it became clear that DB had never really seriously intended to come, or at least not with niece and nephew, as he'd booked them in to do something else (booked after I'd made arrangements) He was out the rest of that weekend so doesn't appear to have been particularly ill.
So as not to dripfeed, relationship with DB can be difficult. None of us were close growing up and we've tried to make it work better as adults, but probably don't have traditional expectations of each other as some families would. However he has always complained about not having family support with having young children (no grandparents on hand due to distance) but then makes it quite difficult to support as he always expects everything to be his way. He's commented a few times in the past that I don't 'get it' because I don't have my own. I have friends with children and have never had any issues socialising with them, I'm aware things change after kids and I try and adapt to that.
I am pretty sure the flakiness was because didn't fit with exactly what he felt the children should be doing that weekend rather than him being ill.
So AIBU to call him out on it, because he should have made some effort for a big birthday, or am I being selfish for expecting anything when he has children?
Fwiw I realise this might read that DB is controlling - it isn't one sided, SIL is the same in terms of liking things a certain way. No concerns about the relationship in that sense.