Well in the last episode Joker cops to Jason Todd’s murder, and I think Harley says at some point that she was with the joker for a specific number of years that I am forgetting. Pretty sure the kiddo Robin is Damian but it could be Tim Drake I suppose. Honestly the writers for this play fast and loose with the canon so I wouldnt get too attached to that shite.
Just laugh at the spoofy in jokes. It’s just a super violent foul mouthed cartoon.