Well, they sure don’t seem to fear him....nor do they hiss or fluff up when he comes to the food dishes. Neither does Ghost of Li’l Bit. It’s a puzzle. I keep thinking that there is some family connection there.
Could be they’ve known him a while in their wanderings around the neighborhood and he eventually followed them to your house. Great that they get along, at least. It wouldn’t be fun having a cat around that wanted to beat up all the others.