oh fred!
I totally see what you were trying to do and I do think that your bro has gone a bit over the top and was perhaps looking for an excuse to say he wasn't coming without his wife (?)
I really think that you have done everything you can as far as the wedding is concerned and perhaps you should resign yourself to them not coming but resolve to send them lots of photos and the video.
I presume that you don't want to fall out with your bro over this and you are feeling hurt that he could accuse you of being insensitive when actually you were being super sensitive? I can see two choices... 1: leave it or 2: write him a nice letter explaining how much it means to you to have them both at your wedding and how many hoops you will jump through in order to enable them to come. You realise that it is not going to be possible but you want to let him know how much you love and value him and you respect their decision (or something along those lines)
As you maybe know, I only really spoke to my bro last year after several years of us not getting on (in a big way) A lot of our acrimony stemmed from them forgetting to invite me to my nephew's christening and I made things worse by refusing point blank to go to my niece's christening because if I didn't go to one, I wasn't going to the other. With hindsight, it was 99% their fault, but I could have done so much to not let us fall out and instead I got stroppy and stubborn and refused to invite him or his family to dd2's christening and as I said, we only just got to be friends again quite recently (and when I say friends, I don't mean "ringing each other up to say hi" friends, I mean "can stand to be in the same room as each other" friends.
So my advice to you, above all, would be do not fall out with your brother, it is a looooooooong time in the making up.
Really really sorry this has happened, it sounds like she has serious issues!
sending cold, shivery Yorkshire hugs your way.