Thanks, all. He is about 5 months old. Had I seen him in the store a week earlier he would still be more intact. They had just neutered and declawed him. It wasn't until after four days that I realized he didn't even have claws on his rear paws.
Ramses and Catrina were intrepid with him the first few days and I kept him in my office with the door ajar so everyone could see and smell each other. He slept in there for 3 or 4 days. Then there was a little paw sneaking out under the door, hoping for some interaction.
Once he started to roam around and explore his new "cage" he was not to be stopped. Fast as lightening, he is. But now he has inspired the other cats to be more active not only with him but among themselves. Everyone is playing and the exercise is great for them. He looks so small compared to them. He had been sleeping by himself at night until last night when he joined everyone else in bed (2 humans, 5 pets - snug) and actually spent the entire night cradled in my arm.
Ramses and he have become fast friends and Ramses holds him down by putting his paw around Amun's neck and grooms him. I would imagine that they will be snuggling together very soon and probably sleeping with their paws wrapped around each other. Amun even likes the dogs, well, at least one of them. Isis gives him "the eye" when he gets on the bed as if to say, "MY BED" but no doubt everyone will be happy with each other.
I'll take some vids in short order to show them at play.