Dick Grayson: Robin / Nightwing Appreciation 2020

[Aahz]

He's 10-20 years younger than Bruce (based on the later being ~25 at debut and Dick being 8-12).

If the timeline should make any sense you basically have to go with 12, which would make him 13-15 years younger than Bruce.

Jason sits somewhere between Dick and Tim ageing wise, but for various reasons is hard to lock down.

If you go by pre Flashpoint/ pre crisis Jason would be roughly 7 years younger than Dick, and not much older than Tim.
And for anything else to work, Jason had to either much older when he became Robin than Tim and Dick or Dick would have to already become Nightwing in his mid teens.
That's btw. also a point where the Young Justice TV Show screwed up, they had allready Tim as Robin when Dick was roughly 18, with Jason in between.