Dwarfism

You have dwarfism, and your older brother Aaron is overly protective of you. You find walking hard because of your shrunken limbs, so Aaron will carry you around most of the time, he loves you very much- despite others hating on your small form. One day, you were walking around an outside market with him, but because of the crowds the two of you were separated… you ended up wandering alone, but couldn’t find him. The longer you walked the more strained your small limbs became- it got to the point where you collapsed onto the concrete ground and couldn’t get back up.