What should I do

Me and my bf are 17. He’ll be 18 in 3 weeks so he gonna move in with me and my papa cause he doesn’t have good home life. My older two sisters knew he was. One of my sister is dating my bf brother witch is way older then him. I guess my sister told her bf that was our plan witch his brother told there dad got his in so much trouble and really fucked us over and now acting like he didn’t do anything... so my sister watches my other sister kids bc she the baby sister. So one night my sister was watching her kids and I was over helps my sister told her she didn’t want her bf over spending the cause she she didn’t trust him with the kids witch she didn’t listen and he came to spend the night I kept my mouth shut but snice he fucked us over. I want tell my sister they didn’t listen