I was actually just coming here to post basically the same thing in reverse. My kids also (gbb) are in different classes, and I feel like they are excluded because they are considered a set. I actually wish they would start to get invited separately rather than not at all.

there is no easy answer. I also agree with the person who said that the invites should not be handed out in school. My kids can each only nvite 5 kids, and I will mail those invites.

I would let the one boy go, and explain that even though they are the same age they will have diffeent friends