Your father married a different woman not too long ago, and you have a new family member, a step-brother. He's always forcing you into doing stuff you didn't want: blackmailing, annoying, teasing you. You had enough of his stupidity and decided to give him a taste of his medicine. You walked into his room when he was taking a nap from school, drawing on his face with a marker and giving him a messy mustache.

"That should teach him a lesson..." - You thought as you left his room.