You could never forget what your brother's or sister's face looks like. You might think the same goes for your cat. However, once separated, Kitty will no longer recognize his siblings. Reuniting long-separated littermates will usually cause a fight.
A Familiar Scent
Smell is extremely important to Kitty. You've seen him rubbing against most of the stuff in your home, including you and his pals. This is how he scent-marks his things. He'll create a sort of map by covering things in his scent. If he catches a whiff of his scent on something, it'll let him know that this is something safe and familiar to him.
This goes for his friends to. Cats will rub against one another and twine their tails, mixing their scents together. Kitty will know a friendly cat because it'll smell like him.
The Nest
When he was a kitten, Kitty and his siblings stayed with their mom until they were around 10 to 12 weeks old. This created a communal smell of the nest for all of them. As long as the kittens all smell like home, Mom will take care of them. Even into adulthood, if they aren't separated, Mom will take care of her babies, grooming them and bringing them choice scraps of food. Siblings are likely to continue to snuggle and groom each other their entire lives if they aren't separated.
Unfamiliar Kitty
Once kittens are taken from the nest, they pick up scents from their new environments. By the time they're reintroduced, two siblings who once were inseparable will have become strangers. The new scents on Kitty's littermate will make them seem like total strangers. This is because Kitty uses his nose, not his eyes, to recognize his friends.
Even a trip to the vet and back can be long enough for his brother to start smelling strange to Kitty. When his buddy returns, Kitty might hiss at him and avoid him until a familiar scent is established again.
Preventing A Fight
A good way to prevent a fight between two siblings or two pals is to mix their scents together. If one cat has to leave but the other doesn't, take Kitty's favorite blanket or toy with you. Before bringing his pal home, give him a rub with the blanket smelling of Kitty. When you get home, Kitty will recognize his own scent and be less apt to start a fight.
Pheromones can also be used to keep Kitty calm. This goes back to how important scent is to him. You can buy artificial pheromone sprays at the pet store that will have a calming effect on Kitty. It's a good idea to spray his favorite napping spots with these pheromones so he's in a chill mood when an unfamiliar cat enters his home.
Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.
References
- The Enyclopedia of The Cat; Michael Pollard
- Gungahlin Veterinary Hospital: Aggression in Cats After Separation