Our kids were older when we had him but he was very protective of the kids. Didn't matter if they were ours or not. When they were here, he felt they were his responsibility and he wasn't about to let anyone get between him and the kids if he didn't know who coming into the yard.
It was really strange that if he was out there with the kids and a parent showed up to pick up their kid, it was as if he knew them already, even if he had never seen them before. I guess he could sense that one of his precious kids belonged to the parent or something. He was a good doggy too.