Hi. I would have to say, I agree with JEN. Just be calm, and know some cats take a long time to get accustomed to other kitties, and yes, he may have to get "put in his place" by one of your other kitties, just to realize where he is and that its HOME.

Just keep trying at it, and be patient. I'm sure he'll come around eventually. One of my cats when I was little that I rescued took 6 months to get used to other cats. It just takes time. Some cats are more loners than others and have to learn to get past the introduction stages.

Keep us updated, and I wish you all the best with Oliver. I just know he'll get used to not being an only baby and realize how lucky he is to have brothers and sisters!

*hugs and scritchies to Mr. Oliver*