Batman headcanon that while typing in a group text format, Jason accidently misspells ‘Bruce’ and types 'Bryce’ as in “I’m meeting up with Bryce later”. Bruce, being the doornail that he occasionally is, asks who Jason’s friend Bryce is. And Jason, being the shit that he is, just goes with it and thus the completely fictional family friend Bryce is born. He is pulled out whenever the kids need an excuse or are trying to get out of doing something. No matter how much the siblings fight, they will always, always, confirm with Bruce or Alfred that Bryce is real and said sibling is really with them.
Of course it gets to the point where Bryce becomes not only more developed but also becomes a projection of all the things the kids wish Bruce would do with them.
“Sorry B, Bryce and I are going out for coffee, we’re going to be discussing our emotions and airing out all of the troubles we’ve had over the years and reconcile once and for all and assure the other that we love and care for them”
“Don’t wait up Bruce, my friend Bryce is helping me with the technology on my computers because unlike some people he values my tech expertize and leadership as more than a disability and doesn’t treat me like a secretary.”
“Ya I’m meeting up with Bryce cause he actually gives a damn about me and he’s gonna murder the Joker for me and then stop replacing me with 10 year olds :)”
“Bryce and I are going to hug, for like, an obscenely long time. I will probably cry big ugly tears that I deserve after all the shit I have been through. It’s ok though because Bryce is emotionally available and let’s me express weakness without the fear rejection.”
“Bryce is teaching me to read, because you won’t.”
“Nah, I can't patrol tonight Bats. Bryce is taking the time to train me himself, not as a replacement or a novelty, but to actually give me some goddamn support and respect and treat me like all the other boys you took in.”
“Bryce is buying me 12 dogs because he loves me.”
Bruce, of course, doesn’t quite get the exceedingly obvious, passive-aggressive hints and just asks Alfred why he’s never met this Bryce character. Alfred just rolls his eyes and tries to think of a way to convey the children’s legitimate complaints in a way that even the oft obvious batman can understand.