Stefan Tasarov is Ari's son. In 2006 Amanda suggested Ari to take his son to game so that Nikita can't shoot him in front of his son.
In 2013, it's revealed that Stefan is under the protection of Krieg, an ex-German special ops officer who was hired by Ari to protect him. Despite the fact that he discovered that Ari was unable to pay for his protection, he felt too attached to Stefan to leave him in the cold. Shortly after he was rescued from Amanda with the help of Nikita and Alex, Stefan chooses to remain with Krieg, but Krieg said there would have to be rules he needed to stick to.