My mom was on a resperator for a few days before my dad told them to pull the plug. She was lucky she had him there to do that for her. She occationally opened her eyes, but there was no one inside... just automatic bodily functions. We all knew there was no real hope of her ever waking up again. I'm sorry you had to be the one to make those decisions for your brother.

I like to think that it's God who decides who pulls through and who doesn't, but there are an infinate number of things that could effect it, from age to genetics to their previous lifestyle. Ultimately though I think the best we can call it is sheer luck. There are so many things we'll just never understand no matter how much we want to.