I have full blood German Rott. He is a wonderful big boy that thinks he is a lap dog. He is about 5 yrs old This evening my wife (who is 6 weeks pregnant) my self, and our 14 yr old son we’re all laying on the couch. Thor the dog was laying across my lap with his head on my wife leg. Our son was petting his head gently just like any other time we pet him. And out of nowhere the dog bit Kaiden on the arm. There has been a couple other instances where he has snapped or acted aggressively toward Kaiden. I am very much Thor’s favorite person in the house. Does anyone have any ideas as to why Thor is aggressive to him.