It's hard, I won't lie, but you just need to say it, there isn't an easier way unfortunately (well as far as i know). At least get the main point out about SI. Then, later on, you can give more details out and hopefully you will get more comfortable with talking to him.
I think that once you get his first reaction, you can work it out from there (not to mention he's your bro, so he loves you!!)
((((((((((paintingravens))))))))))