Wren, I don't know your family, but I'm not sure that skipping into the same grade was what impacted your brother. I was 11 months older than my brother and skipped so that I was two years ahead of him. He too set a lower bar for himself--I was the smart one; he was the athlete.
However, I also think that we were who we were, and that I would have been the smart one and he would have been the athlete, regardless of who was older or younger, and whether I'd skipped or not. I think that would have been true even if we'd each been only children.
I think you have to do the right thing for the individual child.
