What’s funny is that in the eyes of some posters, the bride is being controlling, but it’s not the controlling that’s the problem. The problem is it’s the wrong person doing it:
OP and her mother should be telling her brother what to do.
They and/or the brother should be telling the bride who is going to be in her own bridal party.
They’re selfish to be having their own wedding (that they’re paying for) the way they want, when it should be tailored to what OP/her mother/her stepfather want. In short, it’s selfish to plan your own wedding to your preference, and definitely not selfish to plan someone else’s to your preference.
Similarly, it’s fine to carry on insisting you get your way despite repeatedly being told ‘no’. The person who finally gives in and sends an invoice, along with a note stressing that you paying really isn’t required or expected, is a cheeky fucker because they didn’t read your mind and give you exactly what were expecting, yet failed to communicate in the first place.
It doesn’t matter if the brother doesn’t consider his ‘stepsiblings’ to be family, or isn’t close to them, OP does and is, and that’s what matters. At his wedding.