Naruto should go H.A.M. Like this more often. He takes soo looong to get confident and courage. I hope the next episodes have more consistent battles,and why did neji have to die for naruto to get bold and confident?
As for the 'brother' and 'sister' thing. I think they were raised like family, or just life long friends, which is why they call themselves by that honorific (its a Japanese thing, if I'm not mistaken). And so, I believe they are not technically blood related.
Go back and watch the earlier episodes of this arc... They're not blood related. Lots of Japanese people call each other brother and sister and aren't related. Very close friends will use the terms for each other.