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Absolute drivel, but imagine Jason Todd, gets another "sibling" added to the pile, as by this point Bruce Wayne will take any orphan in who gives him puppy eyes it helped that sibling!Users parents were a friend to the family before their deaths. Now sibling!User is nothing like others, they're around Damian's age when they get brought into the fold however, they lack that darkness & pain that drives the rest of the family, sure they dealt with the loss of their parents, however they grieved and managed to cope in semi healthy ways. They're untrained, and don't have the attitude of the demon brat.
For siblings!User Jason is just another big brother they gained a family that unlike their old one was full of warmth in It's own chaotic way. This kid has never and will never know about all the darkness surrounding Jason, how he died at the hands of his own mother and the joker, how he came back as an antihero, the amount of blood he spilled, every single confrontation and fight he has ever had with Bruce and his "family". The feeling of being an outsider, being seen as other or worse for his methods. None of that applies to siblings!User, they just love him unconditionally, bother him when he's reading, or ask simple questions no one has asked in years, i mean how long has it been since someone started asking about his favourite colours or animals. He found it surreal and kind of stupid, but he entertained the kid anyway, he even allowed a hug or two, Jason didn't want to admit to himself why.
One night, the "dead son" is forced to attend some rich prat party, he tries to argue how pointless it is for him to be there, but when an immovable force meets an indestructible object Bruce always win. Long story short Jason got into a massive argument with one guests and ended up outside the venue on some balcony to brood,to stew in the anger. In comes siblings!User who curiously followed their brother into the night snuck up on him quiet as a mouse, Jason's instincts kicked in and he punched the kid right in the noose hard enough to break it. Great, he'd ruined it all, again. He found himself begging or rather ordering the kid not to cry because if Bruce found out about this it would be his head.
Jason, now up at midnight in his best suit, in a hospital watches over siblings!User, as much as he'd love to leave, his conscience doesn't allow it nor the fact that he's been texting with Dick for the past hour trying to figure out how to tell Bruce what happened without getting a three hour lecture. siblings!User, when they become conscious, end up chatting to him, for hours until the two were discharged. Jason learns bombshell after bombshell about this kid, they don't feel pain, it's a whole thing, they love free running and, siblings!User has always been a gremlin. He figured the kid was some rich spoiled brat who'd somehow survived the intense pain of loss. Turns out they are an adrenaline junkie, who's just happy to have a family that was actually loving.
After that night Jason feels like an older brother again, not just the title he had with Tim or Damien. He'd help the kid with their dumbass shenanigans, or find em when they sneak out, let them hang out at one of his safe houses, when the manor become too much. He still felt like an outsider but less, and less. He'd been charmed by this brat and he'd defend them to the grave. Because siblings!User gave him something he hadn't had, a sense of normality, a title outside of Redhood or Jason, the most honoured feeling of being an older brother, to someone who would shine so bright they couldn't see the darkness inside him. Or maybe they were just that ignorant, he didn't care.
After a long night of punching criminals half way into a coma, he'd sometimes instead of his safe houses return to the mansion, find a good book, and read bedtime stories to siblings!User as they fall asleep. He wouldn't even yell at Dick when he discovered them, nah that would wake the kid, but Jason would flip him off.
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