Hello Hulkman, welcome to UE!
Yes; you can explicitly address a sonnet to one person, two people, a football team, all the people who live in Africa, everyone with red hair, all women, all men, a particular white horse in Sweden, the moon, the people of the future, the people of the past – everyone or anyone!
You can even address a sonnet to yourself.
Then too, sometimes a sonnet has no explicit addressee; in which case, we may say that it is addressed to "whoever reads it".
Student or Learner