On the Empirical for a completely different project, and as an easter egg to boot. According to just about every single piece of evidence available to us at this time, the Starkiller controlled by the player in this game was cloned on Kamino. Even if he isn't, however, that's not relevant to this update; it neither confirms nor denies that Starkiller's the real him. What it does confirm is that clone or not, the player plays as 1138.
As for 1157, it's clear at this point he was a red herring; he's another one of the unstable clones who gets killed by 1138 either when he breaks out or later on, "if" he returns to Kamino.
"There is something going on in time and space, and beyond time and space, which, whether we like it or not, spells duty." -Winston Churchill
"For of all sad words of tongue or pen, The saddest are these: 'It might have been!'" -John Whittier
"Apathy is death." -Kreia