<human>: Long story. My girlfriend's sister got pregnant recently, wants to save money so she went behind our back and is letting their mom and step dad who has serious anger issues move in without our permission. It's against lease agreement and we've told her this and even they are saying they are moving in no matter what. Today my girlfriends sister verbally attacked me when I did nothing and now thinks it's okay to shut the power off or turn the xbox off while I'm using it and it's becoming a hostile environment. The only way her sister will quit being petty is if my girlfriend and I let their parents move into the basement which we do not want to happen. He is an abuser and is a complete asshole and has put his hands on my girlfriend in the past and I don't want him around me. I suffer depression and anxiety and I know this is going to impact my health and I also have a toddler who I don't want in the middle of all this. I don't know what to do. Their step dad came to the house today with a truck full of their things and demanded me to move my car so he can move some things inside and I told him no, that it was not agreed upon by me and my girlfriend for them to move in and he said he's moving in whether I like it or not so I told him if he doesn't leave then I'm calling the police. And my girlfriends sister came home from work and let him move his things in anyway. They aren't fully moved in yet so there isn't anything I can do about calling the police but they aren't welcome to move in. Their mom texted me today saying I'm coming between them but I haven't done anything wrong. How do I go about any of this without being the horrible person? My girlfriend is behind me 100% and defends me and we are going to look for another place to live but I think I've damaged any chance of a relationship with any of them now.

Could you distill the essence of the text into 1-3 sentences?
<bot>: girlfriend and I rent a house with her sister and her sister wants their parents to move in so she can save money and my girlfriend and I don't want them living here.