I think this is a good representation of brothers. The similarities are subtle and not too obvious.
Aren't their necks a tad long though for proportion's sake?

Sweet, they really look like brothers! Maybe the noses differences is too much imo, but it can also be because of the brush width xD

Maaaaan, you gave him a scarf too, and he wears it in a different way than Noah <3

...

http://upload.wikimedia.org/wikiped.....2/Meandros.png

Sorry, that popped in my mind when I was thinking about him. It's one of my favourite shapes, and the concept itself... it's related to water: http://en.wikipedia.org/wiki/Meander

I dunno, maybe it can inspire you.

I'd say they very much look like brothers, due to both similarities and differences. As usual, I really love your expression work.