Almost to the day, 11 years ago, I brought home two shelter cats, a bonded pair. I was warned that they had been "brought back" which was a fair way of warning me that they might not be easy to manage. I figured they were about 2 years old, maybe more.
It was obvious within a week or two that they were utterly terrified of us, even though the other cats were okay. In under a year Sammy had run away once, and then run away again permanently. Toby stayed. I never pushed at him, never tried to shove hin into 'loving' me. He had cat friends here, and would eventually tolerate brushing, and now and then a slow blink from a safe distance.
When we got Charlie some years later they bonded immediately, and I think that helped. He still had a friend. This last fall I noticed Toby was beginning to look like a toast rack with fur, but he refused to be handled enough even to get him into a carrier for the vet. So I did the next best thing. I brought down a litter box, and put it in the dining room, got him some new food, and made up a big carton with squashy pillows in it, next to the stove. After a few months he realized that the human wasn't going to throw him out, and he stopped running away the minute I entered the room. Now he sleeps through Loading the Stove, or even my walking past him. I reach down and talk to him and he allows me to pat his head. Purring. Two days running and he has come out to the kitchen in the morning with his tail high and purring, allowing me to actually scratch between his ears and shoulder blades.
I looked it up, and this trainwreck of a cat is 13 years old. I don't expect too much more time with him, I know he's probably on the way out, but he's warm and fed and comfortable, and he's still got Charlie as a buddy.
Unless I find an elderly cat on the doorstep one day, these will be the last cats I have. It's been a good run; 50 years, 22 cats, no regrets.