The older sisters in the movie are all very fierce and sharp, they always rely on themselves as the older sister - the larger role in the family - to bully the shy, gentle younger brothers. Being told and scolded is something you often have to endure, but there is something much more terrifying than that, which is having to serve your physiological needs, like slaves. That's the sexual norm. The girls say if they lie on top they must lie on top, if they lie below they must lie below, don't dare to go against their wishes. It's true that having an older sister is really difficult, not like what people usually think.