Persuade someone to go out of PS4 party but how?

My friends are in the PS4 party that I often go to. Unfortunately, one of them also has friends who have cousengs and even more friends. The party is flooded with people I don't know even though I just want to talk to my friends. What can I do or how do I get them to stay away (I'm 15 the strangers between 16 and 18) And mute doesn't work because some of my other friends talk to them and that's really annoying.

In this case, I would be throwing a private party to which I would only invite my friends and at the same time not allow them to bring their own friends.