Very cute kids! I'm quite new to photography and especially new to critiquing and such, but I'll give it a try.
I find that few of them are really tight. 1 & 3 are missing feet, and 3 & 4 are missing part of their heads. I'd give them a little more room. I like 5 because it's obvious you *meant* to make it tight, but the other ones don't look like they don't on purpose. All in all, I like no. 4 best. His expression is priceless.
the others are really good too though. Missing body parts in photos doesn't bother me in the least. As long as the composition is still there, tiny bits of head or feet don't bother me all that much.