Some breeds are more prone to same sex aggression than others. Unfortunately the German Shepherd breed happens to be one of those. It is not uncommon to have issues between two males or two females in the same house. Sometimes it can be a small issue that can be avoided or worked through, other times it can be a major issue which can ultimately end in a serious injury or worse.
When you are adding a second dog to your house, it is always a good choice to go with the opposite sex. A male and female are more likely to get along, live peacefully and not have issues in your home.
There are cases where multiple dogs of the same sex can live together and get along with no problems. It really depends on the dog’s personalities, the owner and how the situation is handled.
Generally females are more known for these same sex issues than males. You can have two females live together peacefully for several years and then boom a fight breaks out. Once this happens, you are often never able to get them together again. In situations like this, the dogs will need to be separated completely. This can be very difficult for some families. If you plan to add a second dog of the same sex to your family, you should be sure that you are able and willing to keep them separated if it should come to that.
If you do have two dogs of the same sex, even if they get along well, you should always be aware of their behavior towards one another and take common sense precautions. You will not want to leave two dogs of the same sex alone together when you are not home. If a fight should break out and you are not there to intervene, you could come home to a major disaster and some seriously injured dogs. It is best to simply separate them by baby gates or into different rooms when you are away. Always better to be safe than sorry.
Also be careful with high priority items such as toys, chew bones, treats or during dinner time.
While obedience training will not prevent all situations of same sex aggression, having good control over both dogs will help you to avoid it in some incidences. The more obedience you do with your dogs, the better off you will all be.
Of course when you have two dogs of the opposite sex, extra precautions need to be taken to prevent unwanted breeding. One or both dog should be spayed/neutered, or you should be sure that you are again willing and able to handle the situation responsibly with no accidents.
As long as you act responsibly to prevent an unwanted breeding, your best bet is to always go with the opposite sex.