I have two pit bulls . One is a dog my boyfriend’s mother had but couldn’t keep. The other is a rescue. One is 3 the other is 4mths old. Both have been great about playing with each other but recently I’ve noticed the older one getting more aggressive twitch the younger dog. My boyfriend swears “that’s just how dogs play with each other” but it makes me extremely nervous. I’d never forgive myself if I didn’t ask questions and the older dog bit the younger one.