[quote=@Member 00492]
A good pair of goons is a good pair of goons. Supposedly they were still at it when Terry was older in [s]Epilogue[/s] the JLU eps with Chronos where they mentioned being the ones to kill GL Kai-Ro.
[/quote]

There's no evidence to suggest that the "Once and Future Thing, Part 2" was a long period of time after Batman Beyond's chronological run and even if it was for Batman Chronos was a time traveler who very well could have recruited Dee Dee and Dee Dee much earlier in the timeline.

These are Harley Quinn's grandchildren, even though she'd more or less given up the life that legacy didn't give them any drive to move up over the course of five years?

Which doesn't explain why J-Man is still at it into his twenties.