You were Erens younger sibling. You were young when your parents died. When Eren left, you were officially all alone. But you still had Armin. Eventually, you found out Eren was to be killed. It broke you.

Armin walked into your room. You had tear stains running down your face. Before he got a chance to speak, you did. "Eren's never coming back, is he?"

That hit Armin in the heart. To him, you were like family. "No...he's not. But, don't worry. I'll always be here."