...who is he???

First I want to tell you that I'm in total awe of the theories you people! You notice every detail! I don't... ;-) but that's what this forum is for :cool:.
So I'm sorry if this post doesn't make any sence to you, but I guess my curiousity got the overhand here...

So, we've seen Alex's boyfriend, locked up next to Sawyer...then he asked Sawyer how long he'd have to walk to 'their' (hurley, charlie, locke,.. ;-) ) camp... Then he gets out and frees Sawyer, first of all I'd like to say that I don't believe it was a set up (showing Sawyer he can't escape...I think Ben was the one who made that very clear...)...so he really was locked up, thinking he was still on the 'main' island? But if he's Alex's boyfriend, how come she knows (Alex has been seen on the main island -in the episode where she helped Claire escape :-)) and he doesn't?
Who is he? Why is he locked up?
Is he one of the kidnapped ones? Did Alex met him in wherever they're keeping those kids? Does that explain why he doesn't seem to know about the other island?
I'm confusing myself right now, but this is something I keep thinking about, so I thought I would share it :-)
Sorry if I wasted your time :-)

did alex really escape when she was runnin around with her slingshot or was it all a ploy to make kate think they were gonna really kill sawyer, curious cuz alex's voice comes on the intercom to get jack to open the door and see kate and sawyer on the monitor, alex knows theres 2 islands, and whats the conncection between alex and ben, alex was askin where ben was but juliette told ben on the operating table that she dint ask about him and that she brought her home the day before