See the Friction From Both Ends
The young dog is not being cruel and the old dog is not being grumpy for sport. A two-year-old pestering a thirteen-year-old for a game is asking the only dog available, while the senior who snaps after the fourth bounce is defending sore hips and precious sleep in the only language that works quickly. Most households fix this by changing the young dog's day, not by expecting the old dog to tolerate more or the youngster to understand arthritis.
Watch where clashes actually happen: doorways, food preparation, your arrival home, and the evening hour when the young dog has energy left and the old one has none.
Burn the Young Dog's Energy Somewhere Else
Give the youngster his own programme: a proper run or training session, play with suitable dog friends, and problem-solving games that tire his brain, scheduled before the times he usually pesters. A young dog who has already worked, played and eaten approaches the evening with something closer to the old dog's speed, and shared time becomes the gentle sniffing, pottering companionship that actually suits them both.
Walk them separately sometimes. The senior's slow circuit of familiar smells is not exercise for a young dog, and dragging the senior round a young dog's route does her joints no favours. Separate walks also give each dog time that is entirely theirs, which reduces the competition that spills over indoors.
Protect Rest, Food and the Right to Leave
Set a household rule with teeth: a sleeping dog is not woken, a dog who walks away from play is not followed, and meals happen apart, with the senior fed in peace behind a gate if the young dog hovers. Give the older dog a rest zone the youngster cannot enter, using a baby gate she can be lifted over or stepped past herself if she is mobile, and enforce it kindly every single time rather than only after a scuffle.
Supervise early greetings and excited moments with the young dog on a light house lead if needed, so you can redirect a bounce before it lands on an arthritic spine. Redirect to a toy, a chew, or a trained settle on his own bed, and reward that choice generously, because he is learning that calm behaviour near his companion pays better than pestering.
Teach the Skills That Make Living Together Work
Three trained behaviours carry most of the load: a recall away from the old dog that works indoors, a settle on a mat that holds through family activity, and a leave-it that covers dropped senior-dog medication, senior food, and the old dog herself when she is resting. Train them when everyone is calm, in tiny successful steps, and pay with the young dog's favourite rewards, since you are asking for self-control at the exact age it is hardest.
Keep shared sessions short, finishing while both dogs are still relaxed instead of waiting for the senior's patience to run out.
Expect the Balance to Keep Shifting
As the older dog slows further, the young dog's role changes again: walks together may shorten to a garden potter, play may vanish entirely, and your youngster may need still more of his social life sourced elsewhere. Some young dogs become gentler and oddly careful as they mature into the arrangement, especially if their needs were never left to compete with the senior's in the first place.
If the senior starts avoiding whole rooms, eating less, or snapping daily, involve your vet, because pain makes tolerance shorter and treating it can restore peace faster than any training plan. Keeping both dogs' differing walk lengths, rest rules and feeding spots visible through KinsLe Family Sharing stops a well-meaning family member undoing the balance with one long joint walk.