I have only one and he truly thrives on being the only one, he's very happy. I would love to have more cats but Sash is FeLV positive and I would worry so much about causing him any stress, that's my main reason I don't have another. Sash also has become quite irritated when he's seen other cats outside and attacked me then, so I know he wouldn't take to another kindly.

If your kitty is still young though it might work out, it's really up to you if you truly want another one, but I'm sure he's happy being the only one too.