I understand your annoyance w/ your brother and the questionable circumstances. I have a similar type of brother.
BUT this is still is (at least for the moment) his fiancee and I find it rude to exclude her. It's ONE person. ONE.
Christmas shouldn't be about excluding people.
Hell - for a little perspective, my aunt might die in the next day or two, and if so - Christmas is pretty much cancelled for my family and we're losing someone we love.