We have 2 elder dogs around 8 years old one female and one male. My son came home to live with us and has cancer. We got him a pup that was a rescue just before the dog was one. He has a lot of anxiety and shakes if anyone yells or even talks really loud. The problem started a couple months ago when the play biting tuned more aggressive and I need to stop it before it gets out of hand. I sure don't want to get rid of my sons dog but our dogs can't be beat up by him either. What to do? Help. Most of the time they love each other it's only the male dog.