For all of the same reasons they don't want or cannot keep their mixed brothers and sisters. Up to 3,000,000 purebred dogs are thrown away every year in our country, the land of opportunity. You are looking for a companion animal and a family pet so why not consider rescuing one of these 2 to 3 million dogs. Below are some phone numbers and web addresses to help you begin your adventure. I will start with introducing a new cat to the resident cat.
Cats are by nature solitary and very defensive of their space.
Most of them seem to like their people more than other cats, at least until they set up their boundaries and decide to accept this new idea. You can help the situation along by understanding why they are displaying certain types of behavior. When you bring a new cat into your home he should be placed in a room by himself for as long as it takes for both cats to learn to at least tolerate each other. After a day bring your resident kitty in and let them see each other. They will most likely growl and hiss, unless the newcomer is a kitten.