One thing I have learned over the years is that quite a species of dogs can feel jealousy of a newborn or small children. And the end result is described here.
I was told by my Pediatrician that the largest amount of dog bites to children happen when the child is two to three because the dog no longer see the child as a baby but rather part of the pack.
The dog may well be fighting for it's place.
I grew up with six siblings and 6 different dogs over the years, including 2 huge German shepherds. We were not always watched when playing. No one ever even got a scratch. I guess even dogs are stressed out these days.
Perfect example of my tagline.