Can’t hurt LSAggie! I’ve had mixed success introducing adult cats to each other, sometimes it’s been no big deal, it really depends on the personalities involved!
The grey cat is a very lovable, mellow cat. My Annie, on the other hand, has been spoiled since, well, forever. She was dumped at the vet’s when she was a tiny kitten, and the vet tech’s fed her and raised her and carried her around in their pockets, you know the drill.
Louise was such a mellow cat that as long as her food supply was not interrupted she was pretty cool with other cats. Annie, not so much.