Kids can be hilariously horrible to each other.

In the video above the brother has his cups stacked just right before he gets in place to knock them over, but not before his sister comes along and knocks them over with not a care in the world.

It's funny to me because my younger sister and brother used to do things like this to each other. My brother would have his Hot Wheels and/or Lego's placed perfectly, and thinly sister would smash through his peaceful play are like Godzilla kicking toys across the room. Of course, he got his revenge when she played with her Barbies, but most of the time she got the upper hand and then played innocent.