Your photo of Sambucca as a kitten with Blake prompts me to ask if Blake was used to other cats at the time. I'd love to get a kitten, but my adult cat is very "unfond" of other adult cats. I don't know if a kitten would be accepted.
Haha. So, just to clarify. On that picture Blake was still a kitten himself. I know, I know. He doesn’t look like it, but they were both very young, so it was easy for them to adapt to each other. Blake lived with his family and other cats at his breeder’s place before he came to live with us and about 2 weeks later Sambucca moved in as well, so he was barely ever alone.
In general the chance that an older cat will get along with a new cat is higher with a kitten or young cat, cause also in the animal kingdom the baby-bonus works! But depending on the age or personality of your cat maybe an adult cat might be a better match. I don’t know how you tested your cat’s compatibility with other adult cats, but if they only met for a couple of hours or less than 1 to 2 weeks being “unfond” is quite normal behaviour.
I wrote a little something a while back on introducing a new cat to your household, maybe it proves useful to you. :)