I love the whole Cryptic BatFam thing going around, so I thought I’d put my own two cents into the ring.
They where human once, just not anymore because of Gotham. Gotham isn’t a ghost but something close that feeds on emotion and belief. She saw what Batman was doing and decided to help. Nobody realizes that they’ve changed, as the changes came slowly(because She’s weak and human belief can only do so much), and the effects become almost unnoticeable out of costume. That doesn’t mean they disappear because they absolutely can still do it out of costume if they wanted, but once in costume they have to physically try to act human, they just never notice because they never needed to act human while in costume.
Gotham gives them stuff people believe they can do, She picks what She likes and gives it to them. Someone believes Batman is one with the shadows? Now he blends in even better. Robin is immortal? Hell Yeah, She’s pulling him out of the grave. Nightwing can channel electricity? Yeah he can do that, he just doesn’t know it. Someone believes something She doesn’t like? Veto, denied. People stopped believing them? To bad, She already gave it to them and no take backs.
She made sure to have the powers transferred to whoever holds the title after Jason came in the picture and became Robin, but She also made sure that just because someone is wearing the costume doesn’t mean they can just become Robin or Batman, She has to check and verify that yes you can become them. So Tim just thinks that he just became better at playing Robin instead of what actually happened. This also means that Robin becomes more Other whenever someone new holds the title because of everyone’s interpretation changes with each new variation.
They also created a new language of sounds. Bruce first started it as a way to keep his identity secret by making a whole new language based on rumbles, growls and snarls in order to communicate with Alfred in secret. Gotham saw this and decided to help by making it feel more natural to communicate like this as Batman. When Robin came in She changed him similarly. Instead of growls and snarls it was thrills and chirps. Batgirl has a mix of growls and chirps.
After Dick moved on to Nightwing, he added more rumbles to his speech. And when Jason became Red Hood he changed it similar to how Batman speaks to mess with him, but still used the chirps and thrills from his time as Robin, and a different kind of chirps and thrills as well(yes you know which ones). Tim used more growls and snarls when looking for B so that’s what Red Robin uses now. They make more meanings for the new sounds they create.
You know how human belief can only do so much. Enter Danny. He believed that they were Other. He was Other. That powered Gotham up enough to make it real. She gave them bigger gifts, bigger changes, stuff would have been noticed but wasn’t because it was subtle as it happened slowly, because Danny was still half human. That didn’t matter much when Danny became the fucking Ghost King however. That was enough to make it permanent.
Danny goes to Gotham, and now the BatFam has to explain to a ghost that no they are human, when being as obviously inhuman as possible. And that’s when they realize something’s wrong, because it’s a lot harder to pretend to be human when in costume.
