I need advice.

Let me preface this by saying my best friend in the whole world is Chris. He's been there for me, through thick and thin for last 25 years and me for him. He only has one brother and that's all the family he has left. His brother is a hypocondriac (sp), bi-polar, drama queen and at his core a nice guy. I can only be around him for say 10 minutes before I really start thinking about drinking. Chris writes his brother off once every 2 months or so. So anyway, today I went to Berring to turn in my paper work and somebody at the clinic didn't sign and date something they should and so I had to go back to the clinic and get it signed. I stood, pretty patiently, in line for a good 20 minutes. (this is the point where I realize that there's a "reason" for everything) I get the paper signed and start out the door and I'm nearly run over by Chris's brother who doesn't look calm at all. His brother's lover comes in slowly after and says hello. He immediately says Chris doesn't know. I'm so slow. Know what, I say? He says, that C's brother is HIV +. OK, I won't tell him, I say. Then the lover explains the brother has just gotten his 2nd tcell count and it's dropped from 500 something to 400 something. I do a quick speech on TCells and viral load. His brother has no detectable signs of viral load. That's great, I say. He has nothing to worry about at the moment. The brother comes out and orders the lover inside and we part. I know what's going on. His brother just found out he was positive about 6 months ago and he's been scared to death ever since. Since he's just newly positive he doesn't have all the information he needs and I could provide a lot of it based on my experiences and those of others. But should I? Here's where I need the advice. Do I tell Chris? I don't want him to be mad at me for not telling him when he finds out I already knew. I don't want to lie to him. I feel like I should tell him as my first allegiance is to Chris but, I was asked not to. Suggestions?

Oh well, I guess I don't need your suggestions after all. I spoke to a couple people and they suggested what I already had in my heart. I told Chris last night and he took it well. Much better that I expected. He even said in retrospect he should have known something was wrong because he hasn't seen his brother for the last 6 months. Something always comes up or the brother is sick. So, maybe, in the back of his mind, he really knew what was happening. Progress not perfection.