Why do older siblings make fun of younger siblings?

Not all older siblings do make fun of the younger ones. Some get along very well. Some older siblings would do anything for the younger one. I think it is that the older one has a sense of power and maturity, therefore try to make the other look smaller and less mature so others can see how big they are. Or maybe they don't make fun of the younger one at all. Other times it's the younger one trying to do the same thing. I know my parents always think I start fights, when generally I don't and it's just my sister showing off. So it's a total mix of older ones making fun of the others or the youngers,. I only tease my sister if she says something mean to me. Usually I just comment on the TV shows she watches being made for pre-schoolers. So younger siblings should watch out too- they are often jealous that the older one is bigger and older and more mature and responsible. So everyone should watch out- it isn't just the older siblings looking to seem older.