Wow, you seriously could not have described my situation more perfectly. Only I'm the 15 year old sister, my brother is 13. I do try to take care of myself as much as possible, but he has a lot more problems than I do. His cf affects his sinuses more (he's had sinus surgery already.) And he's had a g-tube, which he's had the worst time with. It ripped out a few weeks ago, and since it causes him pain, he refused to let it be put back in. Now he has to get surgery again, UNLESS he can gain weight without it. Which he's already tried, and not done well. It's not his fault, he actually cannot gain weight, even with tons of food. So, i know he's gonna get it back, even though he doesn't want it.
I have no trouble gaining weight, on the other hand. I don't need sinus surgery yet. But our lungs are both doing pretty well, for now. See, we were both diagnosed 11 months ago, and my brother was only diagnosed because I was, and I was the one in the hospital. He wasn't sick at all. But after his diagnosis, in the past 11 months he's been hospitalized twice. I feel bad for him, because he does take care of himself, and so do I, it just doesn't work out for him as much. We're trying to fix that.