He's Robin during Teen Titans but I figure this after he leaves them, joins Batman for a year, gets shot and leaves batman and starts at the end of the history i put there with Superman telling him about Young Justice. (I don't know much about the DC universe, I'm a Marvel kid.)

*Edit: He could be a watchful protector of Young Justice, A hero they need, but not the one they want.
(Just wanted a dark knight reference in there.)