I understand. My brother abused me and I see him with family twice a year at the winter holidays. I tried to not participate but bent under pressure and suffer through it. I have to deal with the repercussions (bad symptoms and fears) for a week or two after each visit.

I think it is a good idea to set the boundary that if he shows up, you will leave--and end the visit then and there, even if it's your first day. Then you know when to leave and if your parents do arrange him to show up, they are the ones cutting your visit short--they know the conditions.

I'm sorry you--we--have to deal with this. Family abuse is so messed up.