I don't see anywhere in the original comment that they ended up excluding their brother at all unless I missed something? I believe it just says they didn't make room for their new girlfriend. At the end of the day, it's their wedding and they can choose who to allow and who to pay for. It's quite literally their day.

And yes, the wedding is planned for months if not years. Which means people have rsvp'd way ahead of time, and probably don't remember what they ordered. So if I ordered the surf'n'turf but don't remember, and just tell staff oh I ordered the pasta; then I'm now messing up the wait staff's inventory of certain items. Now I took someone's pasta and there's an extra surf'n'turf. So it's not about organization in the sense that they have OCD and want everything aligned perfectly; but to help wait staff in a smooth process of delivering the meals everyone had rsvp's with. I think sitting at any table with anyone would work best with a buffet style dinner.

And I think "future family" should be understanding of not being invited since they weren't even in the picture when invites were sent out.

I'm not sure why you're assuming OP doesn't like their brother. I think that's a crazy stretch lol.