AU where the JLA knew the first Robin and knew Nightwing but never really. Connected the dots.
Clark and Diana know Nightwing = first Robin = Dick Grayson, and Barry knows Dick as Wally's friend, the first Robin as Wally's old teammate, and Nightwing as the dude Wally sometimes gushes about. No he does not know they're one and the same.
In his Robin days, when Bruce revealed his identity, he asked Dick if he wanted his identity to be revealed too. The answer was a firm no thank you.
When Dick was asked if he was Robin, he pinned the asker with a deadpan look and a, "do you really think Bruce would let his own kid go out in that costume? The best I'm allowed to do is man the comms."
Most of the JLA have no idea where Robin came from and are too afraid to ask.
Dick thinks that everyone who needs to know who he is already does—he has his own friends, thank you very much, he doesn't need his dad's friends getting in his business.
So anyway JLA goes to Bludhaven to recruit Nightwing. Dick looks Oliver dead in the eyes, calls him Uncle Ollie, and tells them in no uncertain terms to get the fuck out of his city.
Oliver goes pale, and once they get to the Watchtower, pulls Batman away like "what the fuck what the fuck what the fuck WHAT THE FUCK BRUCE IS THAT DICKIE???"
"He's going through his rebellious phase."
"IN FUCKING BLUDHAVEN? BRUCE I SWEAR TO GOD GO TALK TO YOUR KID OR I'M SIGNING HIS ADOPTION PAPERS MYSELF."
Bruce knows Dick would agree if only to piss him off so he drafts a hand-written letter and sends it. It's basically him apologizing and begging Dick to even consider visiting and to also not let Oliver adopt him because Bruce has had the papers filled for almost a decade now if Dick wants that?
Dick thinks it's the funniest shit and agrees to come home for holidays and a weekend a month if Bruce is civil so he's in Gotham when Bruce comes home with Jason.
Dick loves Jason immediately and demands Jason’s allowed to visit him one weekend a month.
Jason outright preens under Dick's attention so Bruce can't say no without looking like an asshole.
Dick gives Jason Robin after a few months, and the JLA are puzzled to see a new kid wearing the Robin suit.
The new Robin gives them a blank look. "Nonya fuckin' business."
Oliver's biting back laughter because that's the same little kid that begged him to read Pride and Prejudice to him when he spent the night in Star.
They ask Dick if Robin is his new little brother.
Dick looks at them with his age-old deadpan "you're an idiot" look. "Even if Bruce was negligent enough to let him be Robin, do you think I'd let him?"
Tim's even WORSE. Jason doesn't die or anything—he just feels his new ten-year-old genius little brother should be Robin with him and Dick agrees.
I can't emphasize how little control Bruce has over Jason and Tim because they just run to Babs or Dick when he's being annoying.
Tim showed up saying he wants to live with them because his parents won't notice and he knows Batman's identity and hasn't told anyone.
Dick and Jason decide to keep him right then and there.
Tim's quiet, wide-eyed, pale and incredibly small. Half of the JLA think they're hallucinating this new kid because he's literally just a little shadow.
Batman, Nightwing and Robin the elder only acknowledge him directly in soft tones or to direct him, and he never answers verbally—only nods.
Clark and Diana, who know full well that it's Tim under the mask because they were told once it happened, "Hey, is Batman your dad?"
The new Robin stares up at them with creepy white lenses. "He picked me off the streets."
They've learnt not to ask Dick. Jason doesn't answer them. Tim looks like a frail Victorian child and they're scared to ask.
It doesn't help that Tim redesigned the Robin costume so it has pants and the colors are a bit more muted. He disappears for six months (Lady Shiva) and comes back scarily efficient with a bo staff (one that has fucking retractable blades on each end)
Cass is a wraith of a child; small, skinny, never talks, silent footsteps.
Black Bat shows up on patrols sometimes, when she feels like it. The JLA are half sure she's an urban legend.
They don't even bother asking whether Cass is Black Bat.
Oliver's mildly frightened of her, but Cass adores Dinah and barely looks his way so they get along fine.
Dick's endlessly amused by all of this, and has never been happier to have siblings.
Bruce is honestly just happy to have his family together and in one place.
And then Damian shows up.