AIO if Roomate’s Cousin friend stays with us

My roomate is gone for the month so her cousin is gonna take her room while she’s gone. I’ve known about this for a while and totally am okay with it. Im also friends with my roomate and known them for a long time. Couple days ago my roomate said that the cousin was gonna have on of her guy friends stay at the place for a week and this kinda threw me off guard. My other roomate might go home for thanksgiving and maybe me as well but I think it was kinda crazy that the cousin would ask if her friend could stay with us for a week. I think im okay with it but it kinda rubs me the wrong way. If me and my other roomate are not home and it’s just them two then I’d be a bit more concerned. I personally don’t know the cousin or her friend.

What do I do to avoid friction? Am I being overacting if I said no to the cousins friend even if I am not home or am home during this time