I would take the kitty to get checked up at the vet before introducing it to your kitties. You can't really tell if a kitty is healthy by just looking at it and you don't want to risk your kitties getting sick. By looking at the picture it is more likely a male, most orange kitties are male. I'm not really sure on the percentage, but I know that more than half of orange kitties are male.. but it's still possible that kitty could be a girl.