The personality of a dog is flexible and indeterminate. Dogs can be exuberant or shy; friendly or hostile; fearful or bold; aggressive or passive or some combination of the above. These differences in personality may to some extent be determined by breed, or individual genetics, but for the most part it is based on how and to what extent each particular dog has been socialized.
Dogs can suffer from a whole host of diseases and other serious health problems. Some of these conditions are inherited, while others are caused by viruses; still others are related to lifestyle and environmental influences.
Having a dog has been a fun and wonderful experience for everyone in your family. In fact, it has been so rewarding that you are now seriously thinking of getting a second dog. However, it is important that you really think this decision through, because having two dogs can be an entirely different experience from having one.