While puppies are unlikely to instigate aggression from an adult dog, it can happen. Choosing an adult companion allows you to know immediately if you have a friendly match. A general rule is to alternate the sexes of dogs. If you have a male, choose a female for your second dog and vice versa. While this may seem common knowledge, it is not always a predictor of success.
Many male dogs live together in complete harmony.
Some males will fight with females, and some females will fight males. The assumption that females are more passive doesn't always hold true. Some of the most vicious, determined aggression is between female dogs. If you have decided to add an infant animals, you will probably have an easy initial transition. Puppies and adults usually get along within a short time.