It sounds like your 7 year old has poor doggy manners, and the younger dog is reacting to that. I wouldn't call that a reach for dominance. It's just poor doggy social skills. I would keep them separated when you aren't there to monitor them: crate them, or close them in different rooms with doors or baby gates. A behaviorist might have some insight. My guess, however, is that their poor social habits are pretty deeply ingrained at this point.

I'd be careful about attributing aggression to pack hierarchy. The notion of "alpha dogs" is now considered outdated and incorrect. The original research on pack hierarchies was done on unrelated wolves confined to small enclosures. It was like studying a prison gang and then saying that's how a normal family would function. Wolves in the wild don't behave like the wolves observed in the original studies. Normal wolf packs are families: mom, dad, their kid, and perhaps a few other close relatives. They look out for each other like a normal family. Additionally, dogs are not wolves. Dogs have different heat cycles and family structures.

 

Thank you for your response. I don't know if he has bad manners per say, he is very high strung, but he gets along with every dog he meets. I think he has some PTSD from living on street his first 2 years of his life, I am a firm believer in rescuing dogs first if the situation is right but there of course is a risk that you don't exactly know what you are getting.

As far as pack mentality I tend to disagree. I have had dogs for a long time. When I take them all out to walk together they behave much differently, Both males trying to get in front to lead the walk and they group bark at dogs they see. When I take the 2 males out seperately, totally different behavior. Perfect gentlemen, but I appreciate your thoughts. Bottom line, all 3 of their fights are because the older one annoys the younger one by the way he plays. 99 percent of the time they get along great, and often cuddle together.