Hmm.. Good question.(For once) It depends what 你 mean 由 strong. 你 probably mean strength and stuff. He's 16 and appearantly he started working out and stuff. He's probably not the strongest guy to break a brick with his bare hands but he's probably got his line of strength. When it comes to willpower, I surely can't say for sure. He's probably not so easy to crack when it comes to like an mental invasion when someone would try to mindscrew him but 你 never know.