Bruce is Jason’s DAD ok.
I mean Bruce is all of his kid’s ‘dad’ but he’s Jason’s only dad.
Allow me to elaborate.
Dick grew up with loving parents before bruce took him in, and Tim reconnected with his dad as a teen, and Duke had loving parents up until recently and Damian calls him ‘father’ very formally but Dick is also pretty much his dad too (he’s also his brother but still), so like Damian basically has two fathers. But Jason? Jason’s birth father was an abusive drunk who repeatedly beat the shit out of Jason and his mom, and got sent to prison and killed in there while Jason was really little, Jason’s only semi-healthy/loving parental relationship was with his mom Catherine, and she overdosed in front of him so that’s not wonderful but hey at least she never beat him. Sheila was his birth mother but she’s the reason he’s the vigilante representative for why it can be a bad idea to tell people your secret identity, she watched and stood by while he was getting beat to death. So, the others all had healthy father son relationships with other people before Bruce right? BUT JASON DIDN’T. BRUCE IS HIS ONLY DECENT FATHER FIGURE AND THAT’S ONE OF THE MANY REASONS THAT THEIR RELATIONSHIP IS SO IMPORTANT.
This is basically a long winded way of saying that I want Jason to call Bruce ‘Dad’ in canon. Also for Bruce to be very obviously, awkwardly emotionally moved by it because no one else calls him that.