Sometimes the dog is the child....then the real/human/baby/child comes along and things usually change up a bit. I'll admit, I'm always very impressed (amazed, even) when they don't.
Families who make their dog-child a brother or sister of the real/human/baby/child have more patience than I can wrap my little brain around. I love watching it happen though.... don't you?

You can watch them interact with each other here.