Hmm
Batman is older than most of his generation of heroes, but stays in his prime through supernatural things he runs across as a hero. Not by choice.
Dick Grayson was the first Robin and around for a long time before striking out as Nightwing in his early 20's
Jason Todd became Robin II, was killed and eventually becomes the anti-hero Red Hood.
Tim Drake somehow deduces Batmans true identity, but Batman shuns him in fear of him dying like Todd. Drake strikes out as Red Robin on his own eventually earning Batman's respect and a role in the Bat-family as a sort of Robin but not quite full on Robin.
Spoiler/Stephanie becomes a Robin for a short while before being kicked out by Batman.
Barbara Gordon is the first Batgirl active for years before the Joker shoots her and she takes up the Oracle mantle permanently never to return to Batgirl.
Several girls pick up the Batgirl mantle including Cassandra Cain who becomes Black Bat, the BoP girl that was Batgirl for a short time but I forget her name, and eventually landing on Stephanie Brown after she's thrown out of the Robin mantle.
Damian Wayne appears as the bastard son of Batman takes Tim Drake's role as Batman's sidekick and picks up the Robin role. Drake goes off to do teen titans and solo stuff, while being a part time bat family member like the rest.
Selena Kyle is a villain, turned Batman's wife, and occasionally relapses into theft crimes. Bears Batman's daughter Helena Wayne at a young age early in their careers and she becomes the Huntress around 15-16 being taught by Catwoman because Batman doesn't want his daughter in danger.
Uh Batwoman can stay the same just a vigilante cousin of Bruce's.
Relationships: Batman and Catwoman married, Batwoman married to her lady, Nightwing in a serious relationship with Oracle, Red Hood in a mostly sexual relationship with Starfire, Red Robin in a steady relationship with Spoiler Batgirl. Huntress in short term relationships with just random characters.
So Batman and Catwoman are in their early 40's with Bruce being in his prime, Selena being mostly retired but partially in her prime for similar reasons just not as much.
Batwoman probably in her 30's.
Nightwing in his late 20's.
Red Hood in his mid-20's
Red Robin late teens possibly just into his 20's.
Damian 11 or 12
Helena like 18 to 20.
Barbara in her late 20's
Stephanie in her late teens early 20's.
Cassandra around Barbara's age I guess?
And the future would be a bit of both DKR and Beyond. DKR can be Batman in his 60's or so still semi-active, but otherwise retired. Eventually physically unable to be Batman with any amount of technological assistance trains Terry McGuinness to be his successor.
Oh yeah Nightwing leads the original Teen Titans and the older Titans. Beast Boy, Cyborg, Raven, Wally West, Starfire, Donna Troy, etc.
Red Hood dies before any Titans stuff, but eventually comes back and takes over the Outsiders for Batman.
Tim Drakes establishes a new teen titans group with younger heroes different from the old titans. Superboy, Wonder Girl, Bart Allen, etc.
Barbara starts the Birds of Prey, takes time off after shot, and reestablishes the Birds of Prey in many incarnations.
There are ultimately two Superboys. The original leather jacket looking one who dies, and a second clone with I guess similar origin to the New 52?