Decipher this please

[dancemom]

So I have 2 house cats I walk each morning on a harness. Occasionally we see another cat I'll call Big Grey.

Today Big Grey was right outside when I took Boy Cat out. Boy Cat was initially hesitant but then he wandered outside although he did hiss a few times. He does tend to hiss at anything he finds disagreeable though.

Big Grey was miaowing loudly but neither cat had their hackles raised.

I took Boy Cat back in as I wasn't sure how it would play out but can cats ever be acquaintances or would they be territorial and aggressive if I let them approach each other?

Cats definitely have 'friends'.
A few years back when my Charlie was still alive, I glanced out of the kitchen window and did a double-take, because there were two black cats on my bins! One of them was mine, the other clearly a friend as they were laying in a quite neighbourly way on the tops.

My cat has (had, the poor soul died of old age) a best buddy who used to visit daily. Cue nose sniffing head rubs and general fond looks. There's a big ginger who my cat definitely does NOT like!

My old boy was feral until we took him in 11 years ago. He was bottom of the pecking order to the 2 girls were had then. When both girls died, he loved being the only cat in the house and wouldn't tolerate any other cat. He used to chase away any cats that ventured into our garden - until our next-door neighbour got a little female, and our boy allowed her to come in and eat his food, sleep on his blanket, etc. She moved, and now he's back to being intolerant of all others.

My boy is on the left -