Re:A little worried?
I was in the same place your brother-in-law is back when I was his age. I am now 21 and still some what of a loner, expecially after high school when I moved away from home. I have never really had a sold relationship with a girl, or really really dated either.
When I was his age I started getting active in sports and got hooked on a couple of different hobby's.
He needs to find something he like or is good at and run with it. The other kids just have to warm up to him. I would say it was about the end of middle school when the kids stopped bugging me and they started to grow up alittle bit. Yes, people still stare and point every where I go but I just stare right back and point at them and laugh because they are the ones looking like fools and not knowing what they are talking about.
If you sit down with him and get his interest down on a paper, then start getting him active in some thing he will meet friends and succed in life.
Let me know if you need anything else we are all here to help.