u/Fun-Attention8405

I have a really nice gaming computer and my younger brother asked me if he could use it to play some games. I made a new user for him so he could log in and play Overwatch and stuff, but I started feeling kinda paranoid or something and I was thinking that I want to make sure he's just on my computer playing games. I love my brother a lot. I guess sometimes I just feel distrusting of people? I was thinking about putting a keylogger or some kind of monitoring device on my computer. Would I be an asshole for that?