My new lovely kitty is here, and he looks like my cat Beau! They could be twins! Matisse is 5 years old, and really very HUGE. He is much bigger than Beau but very laid back and calm. He's settling in very nicely, enjoying his new home. Beau, on the other hand, isn't sure what to make of this new cat who's entered his territory. He alternates from hissing to being curious and watching him (from a distance). I think he's going to like him more and more as time goes by. No fights or swinging at him, just a bit of fear, but I reassure him a lot and he calms right down. When I go out, I put one or the other cat in my office with a cat box, food and water, and keep the door closed so they don't get into trouble. Then, when home, I let them mingle again.
Matisse loves to sit in the windows and watch the world go by. He's really cute about it, just makes himself at home, happily, and comes to see me when he wants to be petted or fed. Beau peeks in on him, and I can see him from where I sit in the living room, so he doesn't feel alone.
A good thing to have when introducing two cats is a Feliway/Comfort Zone diffuser. It plugs into the wall like an air freshener but has no scent, just a pheromone that calms cats. It works great on Beau, I used it on him when he was brought into my home years ago, and am using it again to keep them both feeling mellow. Matt is already mellow, so the pheromone is mostly for Beau. Breeders swear by Feliway, so it's a good product.
Beau says, "Who's this big new cat invading my house?"