Who is Jack really?

I mentioned in a previous post that there was something special about Jack, perhaps that he was an Other. Well, did you happen to notice that the guy at the end of the show looks exactly like Jack? I have played it over and over and this character is definitely the same actor that plays Jack. Who is this guy? Is he Jacks twin or something? Maybe he's a clone. Maybe they're all clones. Who knows?!?!?!?!

The book The Bad Twin is about a detective who is hired by Cliff Widmore to find his twin brother Zander. Cliff and Zander's father's name is Charles. Charles Widmore was introduced into the show in the season finale as Penelope Widmores father. Could Jack and this other guy be the Widmore twins. Like I said, who knows?!?!?!?!