Who is Marcus Valerius Messalla (Rufus) from Roman Blood and what is their importance?

Marcus Valerius Messalla, known as Rufus because of his red hair, is a young Roman nobleman. As a member of Rome's ruling class, he has the bearing and demeanor of someone much older than his sixteen years. He is the brother-in-law of the dictator Sulla, and he is infatuated with Cicero. Rufus is described as tall with a ruddy complexion, brown eyes and a freckled nose.