Littermate hate - aggression ONLY towards littermates

[Kwilk55]

Hey!  I have a 15m old male BC.  He gets along wonderfully with dogs and people.  He can work while dogs work, watch dogs work (it’s intense, but he can), stand around ignoring dogs, run with them, walk with them.. anything, he’s great and well socialized… until.. one of his littermates enter the picture.  He is then aggressively trying to get them!  Barking, growling, hackles up… they leave, he’s fine.

ONLY his litter mates (he has seen 3 out of the 7 with the same reaction).

I am not worried about how to fix it, it’ll just take a bit longer since we don’t see each other too often. 
I initially thought it was intensity.. but he’s great with some super intense BC’s with hard eyes…  has anyone ever heard of this?

 

[Lawgirl]

I have not heard of this - my experience of litter mates was adopting two male litter mates and they got along great.

I am certainly no expert but my guess would be possibly memories of competition for food or attention from puppyhood, or else feeling protective of you.

It could also just be that something scary or unpleasant happened when he was a puppy, and their scent/looks remind him of that experience, the way some sound or smells can remind dogs of a bad experience years later.

Not sure you will ever get an answer...

[D'Elle]

A very interesting phenomenon that I have not heard of before either. I have seen littermates not get along if they both stay in the same house, especially if the mother is there as well, although more often they get along great. It's puzzling, and as Lawgirl said the answer will never be known for sure. I am glad you posted about it, though, because I am always glad to add one more person's interesting experience to my knowledge. Best of luck with the training; sounds as if you have it in hand.