@Mame,
Update: Milo seemed a bit lonely (he had a friend at his old place) so 2 months ago I rescued 2 kitten siblings (M & F). They were 14 weeks old. I know dogs better than I know cats, and I've never had plural cats... so, I watched a lot of Jackson Galaxy videos... introduced them slowly, had different food stations, etc., etc., etc. From the get-go, Milo wasn't happy. He may be a one-cat cat - who knows? He infrequently hisses at them (and they're not cowed one bit), gives them a wide berth, sometimes gives me the side eye if he sees me petting them... stalks off, but always comes back.
I don't know if this will stay this way - who can predict? I figured that since he's such a chill cat, he'd relent, let it go, whatever, but so far... not.
And today was their spay and neuter day so that was quite funny with them trying to get the cones off, but they seem to have accepted them. Milo did look at them strangely (does he not remember his own ordeal? Or does he?).
Anyway, I know no one can tell me if they'll ever get along, but I would love it if they did. We call him Uncle Milo and hope he adopts/accepts them.
Any opinions or your own experiences? I do realize it depends on the cat(s), but I'd love to hear them.