Is it wrong?

So let's all be honest for a moment... Is it wrong to not love a stepchild as your own? As in you treat them the exact same as your biological children, you are no harder on them, you do the same things for all the kids, you really do everything in your power to keep it all equal and fair. But for whatever reason, deep down no matter how hard you may try to, or want to you simply do not feel the same love for your stepchild as you do your biological children.