My cousin brought his girlfriend to my parents' house, but it was rude. I just don't understand. Don't parents tell him when they know they are rude?

I think it is impolite for your cousin to bring his girlfriend to your house, which is a habit he has developed since he was a child. This also shows that his parents doted on the child since childhood, so they didn't give him a good education and upbringing. This phenomenon is very common in reality. Therefore, a person's good, education and self-cultivation are inseparable from his parents. This also explains the problem of that line. Yes, it is best for children to have a good education from an early age.