Everyone is different in some way. Some people's bones do not grow exactly the same way that yours grow. In some people, their bones grow slower and in others their bones might be shaped differently. That is why people with dwarfism are shorter and could walk or move in a certain way. It is kind of like how your hair style or color, or the color of your eyes are not the same as your friends. It is more noticeable when you see a person who is very short because it is not that common.