High stress in the house

My stepbrother is visiting for two weeks and the tension in the house is super high. My stepbrother is a d*ck to everyone (yes we've talked to him already, he wont listen 😥) my brothers already bad attitude is worse with him around, they antagonize my baby sister which is making her an atrocity, I have to deal with them all most the time so I'm super stressed and ask my already super busy parents for help more then I can tell which is making them exhausted so the house has been a train wreck. Is there anything we, or I, can do to bring down the tension in the house? I'm desperate for any help anyone will offer