There's some interview/archive footage from George and John too. George, in particular, I thought his little bits in the film made him sound almost kind of happy when he was thinking back to those times. After all, those 4 went through something that is very hard for the rest of the world to comprehend--and as stated in the film they only really had each other.
While their group may not have ended the way any of them imagined it would, I don't think it's a stretch to say that they genuinely loved one another as brothers--given what I'd stated above. They fought, absolutely, but they also knew each other better than/just as good as their wives.