Rob, it is rather arrogant for you to say what anyone else feels about their kids or their pets. You are not them, are not in their heads and don't know what attachment they feel for their pets.
And it's completely false to say that just because you squeeze a child out of your own uterus that you automatically love it. There's plenty of folks out there that are living proof they did not and do not love their children.
There is no absolute rule about what a person does feel or should feel about kids(others or their own) or pets(others or their own). How can you possibly say that Person X doesn't love their cat just as absolutely as you love your child? That's just as insulting as if I said you couldn't possibly love your child like I loved my husband. I don't know how much you love your kid or don't love your kid. You haven't a clue about the depth of my feelings or the depth of anyone else's feelings about their pets or kids or potted plants. You can make a decent guess perhaps... based on what tiny amounts of information you might gain from reading a few typed words on a public forum... but that's not very much to base a righteous opinion on.
I've heard the "You'll feel differently when you have some kids of your own..." and it's BS. I'm not having my own kids so it's a moot point and I don't think I would magically suddenly gain a adoration for children by the act of breeding. In fact, if I were to get pregnant I would not keep the child. I'd give it to some person who has the desire for kids. Because I have NO desire to have a kid, a baby, a teen, offspring, children... whatever term, age or formality you'd like to use. EVEN if it squeezed out of my own body.