Awkward situation... Can anyone offer any advice with this touchy subject?

I was out in town a couple of days ago hunting for college supplies and a guy came up to me because I was wearing my college jumper, and he recognised the name of it. We got talking, and he said he'd like to get to know me so he gave me his MSN address. Later, we were talking online and got back to the subject of college. He asked if I had ever met his sister who used to go to the same college, he told me her name and I said no so he simply replied "nm", which I thought was a little strange since he hardly ever uses abbreviations or normal "chat language". But then I realised something and went off to do a little research... And then I figured it out. His sister was actually a girl our tutor told us about.... A girl who took her own life at my college a year before I joined. It makes sense.. On the news article online it says "She leaves behind her brother, Aaron, 18." And that's the right age, since it was about 4 years ago and he's 22 now. Now I feel so bad for him, I didn't tell him I knew what happened to his sister. I'm so afraid that I will, unintentionally, say something to upset him about this.

How do I handle this? Do I tell him or just wait for him to bring it up again?

I wouldnt say anything. Like you said Just wait until he brings it up again. He assumed you already knew and you didnt. You bringing it up means that you investigated and found out...that would make connersation really awkard.

I wouldnt say anything but If he raises the subject, just be honest, say 'yeah i didnt know her but i wasnt sure if you were related so I didnt want to say anything and make you feel obliged to talk about it though.' Theres nothing awkward about it if you're honest and open...you havent done anything wrong by figuring it out here.