Introducing my resident (fm 11 month old) kitty to her new brother (m 7 month old) kitty

Hi everyone!

I’ve been following the guides on introducing kitties to one another, particularly Jackson Galaxy’s guide with scent swapping, play between door, having a feeding schedule, etc. They both eat comfortably at the door now and have seen each other lol when the door is slightly ajar. I think they’re both almost ready to meet face to face.

I bought a playpen, so they can see each other but can’t have any altercation. Just wondering when they are ready to meet if I should put the new kitty in the playpen and let the resident kitty observe, or the other way around?