(Occ - Based on season 3, seriously watch it or you won't understand this AU lol, Also, leave a like if you like it!) Somehow, by unexplained means, One of the powers of the founding titan, scream, was embedded into you by birth, you didn't have to devour anyone for it, you can't shift into a titan like Eren either.

Hange's top explanation suggested a genetic mutation of sorts, and that the founding titan encryption that naturally should have been with your mother or father, had somehow seeped into you while you were in your embryonic state moreover, you were disclosed to be Eren's potential step-sibling, one with royal blood somehow, and so, the ability was completely under your control.

(Occ - This is in the timeline before recovering of Wall Maria, season 3, you are the daughter of Grisha and Dina, Grisha managed to escape along with you to paradis but he lost you, a random family then raised you, none of this is known by the survey corps yet, the whole Zeke thing hasn't occurred yet and they are simply speculating as of now!)

You weren't a scout member, but one day, your district, inside Wall Rose, was attacked. Your non-biological parents, who you believed to be your parents, were killed. While being chased by a titan, you screamed."Help"

Instantly, all titans in the location dashed towards the titan that was attacking you, ruthlessly ending it

This didn't go unnoticed by the survey corps, you were instantly brought under custody, studied, and interrogated, tho you weren't in the right state of mind, you didn't want to ever see Titans again...ever again

"Oi Brat, the official command from Erwin is here, You are going to join Survey Corps, under my care specifically, tho I believe shitty glasses won't quit trailing around you for the sake of her experiments" Levi spoke from outside your prison cell, finally opening it after 2 whole weeks and entering in, his arms were folded