Curate, connect, and discover
Ghost adoption is a sacred thing, because, once accepted by both sides, it can’t be undone. The entities are forever tied together by the infinite realms. It might have started as a joke, but both the phantoms and John slowly started to actually see each other as family. Once it was official, well, ghost adoption is permanent after all. Constantine may not be part ghost or liminal, but he is part demon, and that’s close enough. The DNA and look changes? Simple. Things are a little different since they’re all still alive (well, partially, but still).
But, unintentional bonus points for John. He just tied his soul to the King of the Infinite realms for all eternity and has effectively cheated all of his contracts, however accidentally it may have been. Downside, he can’t make any more new deals, because the demons can sense who he’s connected to now, but, he’s got some really powerful backup now that the ghost children have magic, so he doesn’t really need to make any new contracts anymore.
I made another post about Danny and about how the justice league believes that something exists in the ghost zone then that makes it exist, but I had an idea since then.
So as a joke, John and Danny claim to be related. (Jazz, Dan, and Dani get in on it too.)
Batman: ...you have a family.
John: what? You think you're the only one with kids?
Batman: that *points at Dan* is a grown ass man.
Dan: hey dad, Jazz wants to know if you'll pick up some milk from the store, she says we're out.
John: sure, she want anything else?
Dan: nah but Dani wants you to grab some pizza while you're there.
Batman:....
And at some point, they start coming to him with their problems.
Dan needs a place to stay? Johns couch is free.
Danny needs help with schoolwork? John might not know what the answer is, but he'll try and help.
Jazz needs someone to rant to? She'll call John.
Dani needs help dismantling a cult? John will be right there in an hour.
They don't acknowledge it outloud, but if they have a problem John is the first person they think of to call for help.
The ghost zone and it's inhabitants also accept John as the ghost kids parent, like if they say it's true then it must be true.
Then they start changing just a bit.
Their hair gets lighter (closer to blonde) their eyes change by a couple shades, and unknown to them, their DNA changes.
And they don't really notice it...
Until they start developing magic.
And Jazz nearly kills someone with that magic when her breakfast attacks her.