Well logically thinking, Clark, Bruce, Diana, Ollie, Dinah, Hal and Barry Allen should all be hitting their forties. I'm not sure about Diana and Clark but according to Morrison Bruce is currently 35 and have been Batman for 15 years, Ollie got de-aged after Quiver where he returned to his pre-Hal&Ollie road trip days look, Geoff Johns de-aged Hal to an age of 25 after Rebirth saying the Post-COIE grey streaks he had was a result of him feeling a bit down and since Clark is suppouse to be an year older than Bruce I guess that puts him at 36 and I'm not sure about Diana but that makes her around 34-37 year old. The second of Dick, Donna, Roy and others are all in their early to late 20's. Dick has been speculated to be around 25 and Babara is 27 years old (although I've heard she is suppoused to be 31). The fourth generation of Tim, Cassie and Kon are all in their teens, however, Tim and Cassie are *suppoused* to be the oldest member of the TT, around 18 to early 20'. Thereby making Jamie the youngest with the age of 15.
So to simplify:
First Generation: Alan Scott, Jay Garrick, Wildcat,etc (around 50-60 years)
Second Generation: Bruce, Diana, Clark, Hal, Ollie, Dinah,etc (suppoused to be: 35-45 years, canonically- 25-35)