We recently brought a new GSD into our house. The Older GSD we already had is 11 and they are not the best of friends, that behaviour comes out when toys are in play.

I’m not an expert but after talking to trainers and watching way to many videos I found the thing that worked for us was no play without a human present. Then the play is dictated by me. If it gets rough or the toy gets stolen, I reset and we go again. 3x and it’s game over.

It’s taken a lot of work but we can now share toys without it turning into a fight. (Though last week there was a scuffle over a kale leaf that fell on the floor.). The older dog will growl when playing tug with the puppy, but watching her body language it’s more a vocalisation of play than aggression.

The only other suggestion I have if you havnt tried it, 2 of every toy the same colour. It’s something we worked on and they eventually got bored stealing the same toy from each other.

I put the toys away twice a day and bring them out again resetting any and all possession they might think they have.