My understanding is no family dog will protect property unless trained to do so. And protecting family members is not guaranteed, unless so trained.
A Boxer will protect mothers and children. I also believe they will protect the man of the house, but I haven't seen it like the mothers and children, that's a fact.
When I was a kid, we had a pure bred German shepherd, that was definitely a guard dog, and there was little if any training on our family’s part. One time a city worker with a rake and a shovel approached my Dad and yelled at my Dad, and the dog jumped over the fence and grabbed the man’s arm. I understand he broke his skin. We had to let the vet keep him for a week, but he didn’t have rabies or anything else. He just let that worker know in no uncertain terms not to act that way with my Dad.