Charlie said
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.)
I'm a really big DC fan so if you have any questions then I might be able to answer them, and what GM says is right, this rp is based off of the show Young Justice which is like a mix of the original Teen Titans comics and Young Justice team.