I don't want to listen to my mom complaining about my older brother
I'm trying to understand what is it about her complaining that annoys you.
That's okay, I hate it when she does that.
You shouldn't be expected to always hear about your brother's issues. You should talk to your mother about this so she would stop doing it.
Mom's are always bitchy.
It's fine to not have to deal with your families problems, and it is smart to walk away from it sometimes. You're dealing with it just fine!