I've had the long hair for 6 years and recently adopted the short hair (2023). This is the closest they have been to each other since. So much for getting another cat for companionship. I do work with them to try and build a relationship, but cats will be cats.
Acquaintance has an older female cat, first they adopted some other cats which she wasn't thrilled about, then her BFF died :( She is a one-cat house now and very happy. She still gets upset if other cats come around (fosters etc) :(