Is forced to have anal sex with her brother-in-law and his half-sister

Me and my sister we were never very close. I left the house a long time ago and she was married very young, between the other, with a man much bigger than her. Recently I became homeless, so I asked her to let me stay at her house for a few days. Not wanted, but the husband has invited me to stay. So I used the invitation, even if immediately after I found out why my sister did not want to do it. Her husband is a psychopath controllatore, and my half-sister was his sex slave. During the days I was there, I could not escape, I had to do everything he wanted, and also a threesome with my sister and anal sex.