OK .... here's a question then.
I'm on facebook - but don't really use it so don't quite know how it all works.
However, my friends get invited on by me and then my friends, friends can invite me on to them.
So - do any of YOUR friends talk to this chap at all. If not, maybe they could invite him on to join the circle... and see how it goes for a while.
Remember, his friends are exactly that.... HIS friends.
I know I sound distrusting - when actually (as folk here know) am not - just, he sounds a little pushy to me on the 'ole sex thing!