They're Scottish Folds, and the same mutation that makes the cartilage in their ears folds affects all the cartilage in their body. So they have joint problems and arthritis and also tend to have some other problems. It's not even like getting a breed that "tends" to have certain health problems; the ears are literally evidence that they do. The Dutch government recently banned even owning one (exception for people who got one before ban) and big UK pedigree organizations won't register them.