Lucas has said in interviews that Han was an orphan who wound up on the Wookie planet Kashyyyk, and this is how he wound up meeting Chewbacca. What I don't know is whether Han was actually raised by Wookies and what his relationship was with Chewy -- brother? Friend? I got no idea. Whether they'll flesh this out in the upcoming movie is a good question. We know that young Han will be meeting young Lando Calrissian, since they already released the casting information.