I think another thing people should take into account when talking about the Titans age, family and children is that being 20s something in the 80s is very different than the 2020s. 20s something now have family and kids later than ever and are basically older teenagers be yesterdays standards.
Definitely late 20s, else Dick would be too close in age to the other Robins (Tim's the one who should be in his early 20s, if they actually aged him up the same way they've done Damian).
While Lian was the result of a teen pregnancy, she's now a teen herself. That would mean Roy should be around 30.
Jai and Irey aged up fast like Bart, they'd be no older than Karen and Mal's kid otherwise.
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Dick's generation definitely should be in their late twenties to early thirties as well as Tim's generation in their early twenties.
All of this children talk makes me want to see an elseworld book called The Titans of Tomorrow or Teen Titans Beyond, where the Titans are now parents and their kids wants to be superheroes much to their dismay, that way we can see characters such as Nightstar, Ceridan and Cube (Cyborg's kid) alongside with the West Twins and Lian Harper.
If both Wally and Roy have kids aged ~10 the adult Titans should be in their late 20s/early 30s. I know Wally's kids got aged up, but that's rarely acknowledged (as it usually happens in those cases).
Beast Boy and Raven are the exception because they were teenagers during N52/Rebirth, but all the others can perfectly be in that late 20s-early 30s age range.
Gar and Rae have been aged back up - while Raven did have the death and resurrection excuse, there's no way Garfield should be younger than mid-20s (he's two years younger than Dick, Donna, Wally, and the rest of the original and New Teen Titans).
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The funny thing about Lian being much older now is she was only five before her death.
The aging-up kids thing is only done to open up storytelling with them; mid and pre-teens add more than a baby. When it's done to everyone's kids, it starts getting ridiculous.
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I would even be happy with a webtoon/elseworld with that kind of setup. As well as seeing how their families are doing. My only thought would be; would Damian and non-aged up Jon be included in that generation or a little bit later? Simply curious. And no, I don't want to see a DamianxNightstar. That's a no-no.
Thinking again... alt-future, possible timeline Titans.. could have Lisa Kent(daughter of Superman on Earth 91) and Brainiac's daughter(Kara Zor-el's daughter in Kingdom Come).
you don't need to use them at the age they were last seen in. 'cause well... this could be done as a "similar to" universe, not a direct copy or continuation. also... hard to figure out how you'd have both in the SAME universe... given what happened in their universes.