I can't even remember now who was asking about how to deal with the other non-CF siblings. At any rate, this is a topic that is of interest to me. Having a chronic illness and one as scary as CF is VERY hard on the other siblings. It has affected both my sister and my brother's entire lives. I came from a very nurturing and loving family.
CF can function like an alcoholic in the family.
I will explain how this worked in my family. I know everyone's experience is different. This is just mine. I was diagnosed with CF when I was 6 months old. My sister had no choice but to fade off into the background as far as all our relatives were concerned.