I was a cat person as soon as I met my first cat... that would probably be about age 9 or so, when my grandparents dumped two barn kittens on our doorstep. Tiger--despite her unimaginative name--taught me how to speak Cat, and I've never looked back since. She died while still a kitten, because my mother dumped her at a friend's farm and she got Feline Leukemia, and when she began showing symptoms was put to sleep. My mom tried to keep this information from me, but I overheard her talking to the vet and cried for days.
It still makes me sad now--Tiger did so much for me; she not only helped me learn what cats are all about, but she helped me recover from my first stepdad's erratic, often abusive behavior and was the first "person" to show me not only unconditional love but unconditional kindness, and didn't expect me to act "like everyone else", just took me at face value... Only a kitten, and she did all that! I wish I could have been there for her when she died; and that I could've kept her from being sent away to that farm. Life just wasn't fair for Tiger.
I did technically know a cat before Tiger: We had a cat when I was a baby in Germany; her name was Katike (pronounced "cutty-KEH"), but when my dad died when I was two, my mom gave her away to a relative, so I don't have any memories of her. My mom says she loved chewing up cardboard boxes.