I don't care about my brother's toxic relationship
What makes you think that the relationship is toxic?
He fell for a girl that doesn't even have manners!
I'm sorry that happened to your brother!  However, it's up to your brother to determine whether or not he's making a mistake.  It's not up to you to determine whom he decides to be in a relationship with.
It's ok, I'm used to my brother's actions, he'll figure his mess out sooner or later.
I know it can be hard to watch someone you care about be in a toxic relationship. But your doing the right thing by letting your brother realize this on his own.