Very little is known about Stolen's past. It is known that he lived during the period in ancient times where the Babylonians were still flourishing on Earth and living on Babylon Garden. Given his title, it is possible that he was one of the early descendants of the ancient Babylonians.
Having ascended to leadership of the Babylon Rogues, Stolen was a member of a society of thieves who traveled the world seeking treasures to steal. When the Babylonians invented the earliest form of Extreme Gear, a Magic Carpet. Stolen viewed it as their "ultimate invention", believing it would make their lives as thieves much easier. When the Magic Carpet was put away inside Babylon Garden to be protected by the Babylon Guardian, Stolen left a note with it, stating his thoughts about their creation.
The word "stolen" is the past principle of "steal", befitting the main act of the Babylon Rogues.
↑ 1.01.1Sonic Team, Sonic Team USA (17 March 2006). Sonic Riders. PlayStation 2. Sega. Area/Level: Babylon Guardian. "Dr. Eggman: Let's see... Ah, this looks interesting. "At long last, we've completed our ultimate invention. With this, our lives will be easier, without the need to work so hard to keep ourselves flying. Stolen, the 13th leader of the Babylon Rouges..."