How did you treat your brother or sister?  I think I was mean to my brother. I say "think" because I don't specifically remember being mean to him, but I do remember him chasing me with an ax.

So how about a brother showing you an "in progress" example of being mean?  The video is quick, hilarious and harmless.  The sister, well she's bound to be pissed and will probably seek revenge at some point.  Here's "How To Be A Mean Brother".