Flatmate's boyfriend

I moved out of hostel and shifted with my friend. I was aware that she has a boyfriend but i wasn't aware that they'll be doing live in. Since the day I shifted, the boyfriend also started living with us. Although I have a separate room, still i feel uncomfortable because now my friend doesn't talk with me. It feels like strangers living

You need to move out….they’re just using you to help pay their rent.

Okay so the thing is, my flatmate's sister will be shifting with us from Jan. She doesn't know this, that the boyfriend stays with us. Once the sister comes, I'll be sharing the room with that flatmate. And the boyfriend will also move out, because obviously he is not allowed due to the sister