quick question about cat introductions

hello

my brother just moved in recently with his little female cat


the house hold is so busy and wild the new cat has met (my cats) there wa no hair flying HARDLY any hissing maybe just a sour face but that was it. The new cat is pretty small doesnt seem intimidating i guess to the other cats so they really dont care about her. PLUS she looks exactly like my cats sister maybe thats what helps? ANyways she just got here yesterday but my brother wants to let her have free range of the house cause she likes to "explore" do you think since shes already met the other cats its pretty safe? Let me know thnx

Sounds like a great start, but until you've spent a lot of time (days/wks) seeing them interact, I wouldn't let her unsupervised around the others - she is smaller, and you're not really familiar with the other cats yet enough to predict anything.

Slow intro is usually best but the truth is, we never know what's going on when we're not watching even after lengthy intro. Maybe a good idea to have the newcomer separated at night while all humans are asleep. They come alive at midnight ... then again around 4:00am.