Bart becomes a Legionnaire AU where Iris (Time Trapper in the future) tried very very hard to convince Meloni to send Bart with her to the past "Because that's where his destiny is and you can't protect him from your father so long as he is alive!" and Meloni just went "BET" and refused to part with Bart (he does not have accelerated aging).
This naturally distresses poor Iris because she knows very clearly what Bart's history should be, at least she's pretty sure anyway, and if they deviate from it then they could be at fault for changing history which could result in millions dying that never should have, or even reality collapsing in on itself because of Bart's specific powers.
Iris isn't proud of it, and sees it as a necessary cruelty for the sake of trillions, but she tries to kidnap Bart as an infant with.... disastrous results. Meloni doesn't fuck around, the second she tries Meloni is on her ass, pinning her to the ground, ugly crying, choking her, screaming that all she wanted was to hold onto a family and she was all she had left.
Iris (seeing stars from another dimension from the beating she just took) just slurs it's bigger than them and their love - love doesn't conquer all, love is not the most powerful force in the universe because if it was none of what happened to them would have happened.
Meloni can't bring herself to send Iris away forever or arrest her, but she does make her swear to never do this again.
Reluctantly, and miserably, Iris does promise Meloni she won't try this again and she keeps it, until Bart is 14 where she tries to convince him that he needs to live in the past.
It doesn't go over particularly well either and she just begins to panic because can't they understand this is bigger than all of them.
She doesn't have the heart to try to physically force him to the past, yet, that's something for Time Trapper (her future self) to do. Because she does love him, she doesn't want to do him, and she just like Meloni doesn't have much family left.
This puts a lot of anxiety on Bart, particularly when he (with the rest of his teammates) are shunted to the past during one of many of their adventures because what Iris told him never left him. He's terrified he won't make it back with them to the 31st century. Terrified he won't see his mom or his cousin again and Iris was right all along.
