In The Force Unleashed, Galen is 17. Since it's set in the year 3 BBY, we assume he was born in 20 BBY, during the height of the Clone Wars and not long before Order 66 was issued. Starkiller in The Force Unleashed II is a direct clone of Galen Marek at his death. It's set in 1 BBY, two years after the first game. Therefore, confusingly, the clone is technically only a few months old, developed two years after the death of Galen, and appears to be a 17-year-old.