Sounds like the golden needs an “off” button. Is he young? Over exuberant dogs can really annoy other dogs, to the point of other dogs trying to ‘calm’ the exuberant dog themselves. Unfortunately, this can lead to other issues if the exuberant dog takes offense that other dogs are trying to teach him manners when he’s ‘just trying to play’. I’d guess that this golden may not have been socialized enough to other dogs. He doesn’t know how to approach or play properly and gets too “in your face” with them.
Biocoastal offered great advice. The trouble is that it’s your sister’s dog. Does she the problem with her dog’s behaviour or does she think it’s fine? Personally, I’d be embarrassed if my dog behaved in such a way that the resident dog would stay outside but I realize not everyone would feel that way. It’s going to be harder unless your sister is on board with everything.
Actually, that was one of the things I had to work with on my dog. My parent’s border collie was elderly and frail and didn’t want any young retriever nonsense. He’d get taken for an hour walk with his backpack on before we went to my parent’s house. He stayed on leash while we were there. If he chose to interact politely with the border collie, he was allowed to be near him. If he got too wound up and started bugging the border collie, I’d correct him and he’d get put into a down stay until he settled. Eventually, he figured out that if he wanted to be by the border collie, he had to go about respectfully and calm.
I think I’d try to walk all three dogs together the next time they’re all together. Leash them up, then go on a brisk 60 min walk, letting the dogs sniff each other’s hind ends, but not face to face. Rotate around so one dog can smell the other, then change positions. The walk/surroundings will distract them from each other, but they’ll still get a chance to safely socialize. The walk will put them in a “pack mentality”. When you get home, have the golden stay on leash IF the other dogs are calm as well. It’s not fair to let the other dogs play and the golden to be on leash and frustrated. Keep golden on leash if other dogs are calm and then correct him if needed. This works particularly well if the other dogs correct him first, and then he gets a collar correction from his person to back up that he needs to listen to the other dogs’ signals. His continued ignorance of dog to dog body language might get him hurt one day if he tries these antics on a strange dog.
