Stepsister used! Porn for his mates!

In the morning, my stepbrother told me that he was coming to see me later that day. He wants to make a film and I should do everything he says without even saying anything! So that his mates can see how he can fuck his stepsister and that she does everything without comment! Oh man, what am I supposed to do? I don't want to disappoint my stepbrother, so I just go along with everything. He must never find out that I'm already horny, who knows what he'll do to me!