This is series of fic's I found over at TTH.
It starts with "Wish Granted" then "Hall of the Mountian King"
and then "Long and Winding Road" by Scorpio. The 3rd fic is
still in progress, but the first two are okay to be read by
themselves.

Summary: This series came about due to my fascination with the
situation that Jack's teenaged clone found himself in. I could barely
fathom how alone he must have felt... so I gave him a friend: Xander
Harris.

http://www.tthfanfic.com/Series-142