The balance in a household has everything to do with what the humans are willing to do to make a multi-dog household work. Many breeds do best with opposite sex dogs.
We don't recommend siblings, especially of the same sex. The dynamic breeds rarely do well with same sex or in large groups of dogs in the same household. The hound breeds and breeds that were bred to work in large groups work better in a multi-dog household - usually introducing a puppy (or at least a dog under 6 months of age) of opposite sex to an adult that has been an "only dog" is the best choice.
Many people feel their dog "needs a friend." Chances are good that the dog is perfectly happy being the "only dog" with people as its "pack."
Similar activity level helps dogs entertain themselves - "a tired dog is a good dog."
If you have a sense of humor, and are willing to adapt your lifestyle to a group of dogs, you will never have a dull moment. Carefully create the "pack," paying special attention to who is in charge.