I have two cats, and I'm an animal person--I'm squicked out over human births but a puppy or kitten birth on Animal Planet will get me any time.
Contrary to popular societal belief, though, my cats are NOT replacements for kids, TYVM. I have no doubt that for some people, they are and it really is true that they have a repressed desire to have children and are channeling it into pets. But some of us just like animals, and just because someone may have a bit of a nurturing personality (I really hate the word "nurture" because it's so associated with "aw look it's a soft, sweet, hovering, but wussy and weak mommy-woman"... but unfortunately, I've not yet found another word that is totally parallel to it that I can substitute) doesn't mean they want or need to nurture CHILDREN. Friends, family, and pets (not to mention total strangers) will always need us as well and those avenues may be where our nurturing sense lies.