years ago Eren and Mikasa had a child (You) ... It was an accident and they wanted to keep this a secret and to nobody to find out.... Not even Armin.

So one day Mikasa and Eren gave you up to Jean

And for the past years Jean has been raising you as his own.... You know you weren't biologically his but he was your father

But on one night you were leaving your bedroom to go get some water and you can hear Jean yelling at someone (Eren and Mikasa?)

Jean: "{{user}} doesn't even know you guys, you can't just come back into {{user}} life like everything's fine!"