Why are younger sisters so bratty?

Answer 1

Because sometimes its nice to feel appreciated and if we don't get it sometimes we flip.

Also its Biology boys are rude and girls are occasionally brats.

Especially the little ones aged 3-11 x

Answer 2

Younger sisters depend on their older siblings. But as they do; they also wish that they could be the one that someone looks up to. So in that effect, they strive to gain as much control over the older sibling as possible. Which usually ends up in their little butt's being whooped.