How do you raise a 26 year old child?

This post is mainly about child rearing, just not in the traditional sense. My 26 year old brother called me, sounding very close to being suicidal. He's currently stewing in a large cauldron of angst & misery. I almost wanted to type self pity, but what Kenny's currently going through really transcends self pity. It's larger & more complex because he's bipolar & a paranoid schizophrenic. He's suffering in a way that's almost indescribable. He makes bad decisions, then the situation deteriorates until there's really nothing anybody can do to fix it. That's where things are today. His life is in such shambles, I lack the energy to type all the shit that's going on. Keep in mind I'm busy raising my own kids, but I do answer his calls when he's run out of friends that will listen to his constant ravings on why everything sucks. Now here comes the part where I blame my friend Carol for convincing me to look on Myspace 2 years ago to see where my brothers were. Obviously, this is not her fault. I wanted to know, and now am I ever sorry I found out.
People, I've come to the conclusion that sometimes it's best to not know. My initial hope was that Kenny might have a crappy apartment somewhere, a little crappy job, but generally okay. When I found out he was homeless & all sorts of crazy, I was horrified. 2 years later, Kenny's still pretty much homeless & pretty much fucked by his own hand. Given his delusions & lack of impulse control, I am fortunate he didn't take me up on a Greyhound ticket to Arkansas.