He would definitely know the identities of the YJ as they are all open with each other about their identities expect for Robin. As for the League, Manhunter and Superman would be good bets. Captain Marvel too since both teams recently found out about him being a ten year old
I wonder what the implications are that Cheshire was constantly putting the moves on Red Arrow even though she knew she was a clone and was privy to his kill phrase.
"A fast low flying Power Girl could take out a platoon of soldiers without even throwing a punch."
-someone on the DC forums