My mother, oddly enough, owns my dog’s full-blooded little brother from a following litter. The two dogs recently met each other for the first time when my mother kindly took my dog in when I moved out of state and couldn’t fathom having my dog in an apartment with me while I spread my wings for a few months. It was hard leaving her behind, but she gained a best bud in her little bro and it made me wonder, do dogs know their siblings if they’ve never met before?
My dog and her little brother are so goofy with each other. My dog typically can’t stand other dogs, particularly males, but she and her brother get along like they’ve been litter mates all along, even though she’s about 2 years older. They even act alike, burying bones with air in plain sight and barking in a weird talking way (like how huskies do). They do the same digging at blankets for a bed to burrow in, both get into the garbage and then hide from their mess, they both pee a lot when they’re super excited all over the floor, and they both curl their lips up in a “drr” expression and cock their heads to the side when they’re curious about something. Both of them are afraid of thunder and lightning, both of them cuddle with stuffed toys and collect rocks from the canal, and they both like their butts scratched in the same way, and drag their butts on the carpet at the same time like they’re racing, biting at the air in sync. It’s uncanny the resemblance in both behavior and looks- they look like twins in the face, even sharing one blue and one brown eye. It’s almost creepy.
They ACT like siblings- so do they know they’re related? Apparently, they do- sort of. The same way that dogs know that another dog is not suitable for mating with (such as a sibling) is the same way they may be able to detect if they are related. Dogs are extremely sensitive to pheromones, produced by humans, other animals, and especially other dogs. It’s how they communicate with one another. It’s also how they can detect fear in humans. So a dog may be able to tell a dog is not a mating companion (such as a sibling or parent), even if they cannot exactly tell they are related. Basically, my dog knows that she can’t hook up with her brother, but may not understand that she is related to him.
So does my dog know she and my brother are related? According to the pheromones both dogs can detect in each other, they can at least tell they should not be mating. While I could find nothing that said dogs know each other as relatives, I did find that they can tell if there is some type of scent that tells them naturally they should not be “hooking up”, which is I guess as close to recognizing familial relations as dogs get. I guess the assumption is up to the owner, and in my opinion, I think they just happen to get along famously because they have so much in common. I really don’t believe they know they are full-blood siblings.
Sources: personal opinion