What a sensible young woman! She has put up with being embarrassed by the behaviour of her divorced parents for years, apparently, and is unwilling to have her wedding turned into a nightmare.
So, you and her brothers need to respect her decision and try to get over your hurt feelings.
Invite her and her husband to a nice meal when they come home from their honeymoon, if they are having one, and let her father and step-mother do what they want to mark the occasion.
Ask her brothers if they want to be present at your do, or if they feel that will rock the boat vis á vis father and stepmother.
Orchids and other lovely plants that don’t need a lot of attention


I might have felt differently if, say, in-laws had been invited and we hadn’t, but I think it’s lovely that young people are confident enough to have the wedding they want, instead of what pleases other people.