We adopted the puppies from the county shelter (NOT from a breeder or somebody we knew) at 8 weeks of age, and we decided to get them both because we were under the impression that the two would keep each other company during our absences, and they could "grow up together".
Many people do think that, and end up with dogs who must be separated 24/7Getting two is fine for cats who have no social structure or hierarchy.
Dogs are pack animals with a strict hierarchy, but in the pack, one dog is the "top dog" and the others are subordinate to various degrees.
Dogs learn their place in the pack while still puppies, but in the home it's different. Since it sounds like no one in your home is willing or able to be leader(that is not a criticism - it takes a very knowlegeable person to raise siblings) each of your dogs will battle for that position. Since they sound evenly matched in temperament and size, these battles could be fatal if neither is willing to back down.
So you are right I own greyhounds how can I possibly know anything about GSD's and give advice Many of the dogs I owned were adopted as special needs due to behavioural and or medical problems and I aslo raised a few from pups, much of what the owner is describing I has seen and dealt with.
I was not being critical. You are obviously a very experienced and dog-knowledgeable person, able to deal with extreme behavioral issues, which the original poster is not.
I know many people who have multiple pit bulls, some of whom literally want to kill each other on sight, but these owners also are experienced and able to deal with this aggression. Not everyone wants to, or is capable of dealing with such things. I have a pit bull also and have only one dog because I also want peace in my home. A first time dog owner, like the OP, would feel very panicked and helpless at the actions of these dogs and primarily there is the safety of her children to consider.
For THIS particular person, I still feel rehoming one of the dogs is the best option. A home with no dogs, or with a submissive male dog, might be fine.