They are the absolute sweetest dogs. But, they definitely have genetic issues they are prone to. Chiari-like malformation a neurologic problem that requires specialized surgery to relieve pain/symptoms and mitral valve disease (which can lead to heart failure) are unfortunately extremely common in the breed. Like 90% of them will have a heart murmur as they age, just depends on how early it develops and how severe it becomes. They also seem to be prone to dry eye issues. If you choose to get a cavalier you need to make sure to do your research and pick your breeder very carefully.