I am pretty sure they are suffering from littermate sydrome
k9behavioralservices.com
the dogs should NEVER be together ideally, or a few mins a day TOPs, seperate them asap. I'm not sure how to raise them fully and when they can be re-introduced.. Im sure somebody else here can help.

Littermate Syndrome | Canine Behavioral Services
Littermate Syndrome (also knows as Sibling Aggression or Littermate Aggression) is a non-scientific anecdotal term that refers to a whole host of behavioral issues that tend to present when canine siblings (Littermates) are raised in the same household beyond the normal 8 to 10 weeks of age...

the dogs should NEVER be together ideally, or a few mins a day TOPs, seperate them asap. I'm not sure how to raise them fully and when they can be re-introduced.. Im sure somebody else here can help.