I am sorry that your parents allow your brother to behave badly. Your brother already KNOWS your parents won't stop him or stand up to him so he will continue to behave badly and be this man child. It's pretty sad that your brother finds a need to be such a jerk to feel "revelant". Your parents are showing you that they don't know how to stand up to him. Telling you to put up with him and accept him for what he is is a copout.

What you need to do is sit your parents down and tell them flat out that if they can't set boundaries in their own home and stand up to him and show him that his behavior us rude and unacceptable then you will no longer visit them when your brother is around.

Your children need to know what to do when a bully is present.