I need other opinions

So my boyfriends “brother” lives with us and he’s alot younger than us. He’s 19. He is all about partying and getting with different females. He just had a girl here two days ago. Well today he brought another girl here and I just don’t like this girl. She recently was in a gangbang and gladly posted it all over snap chat. I have my kids that live here and don’t really think it’s appropriate for a bunch of random young girls to be in my house. I talked to my boyfriend about it a few days ago and he agreed with me. Well now he’s saying “if my brother is dating her we can’t be assholes and tell him she can’t be here” I’m sorry but obviously they aren’t in a serious relationship if he just had someone else here and this girl was getting banged by a bunch of guys. Do I have a right to be upset? Or do I just keep my mouth shut in my own house? If I didn’t have kids it would be different but my kids are all young ages and get attached to these people. Also since it was brought up yes we are in a pandemic and it DEFINITELY bothers me. I have 3 small kids and I’m pregnant with baby #4 but like I said when I say something it causes an even bigger scene. Literally feel like I can’t say shit in my own home.