I think your family have been stubborn and rained on their parade at every opportunity. Can't you just be happy for them and let them take the lead sometimes?
You might think your kids would be fine for an engagement announcement but it wasn't your call, your only decision was whether or not you could do him a tiny favour (babysitter) when he asked - which you didn't. If he'd wanted your opinion on your DCs attending, then he'd have asked for that instead.
So, you turned his nice surprise engagement announcement into a critique of his plan and didn't even try to get a babysitter, just pushed and quizzed him until he felt it was ruined and announced it by phone instead. When he did, you didn't even congratulate them - no wonder SIL didn't want to come.
Then the wedding was also about what you wanted, not her, but you got your dad onside as well.
Your brother is as important as you are in the family. I'd be interested to know how you announced engagements, pregnancies etc. and if he managed to be happy for you and let you take the lead. If he did, you need to reflect on the balance in your relationship, do you think of him still as a little brother? He's a grown man now, treat him as one.