Solo was the leader of a group of orphans living on colony V08744. In AC 187, a virus broke out on the colony, but the vaccine was reserved for the rich. When Solo contracted the virus, his best friend sneaked into an Alliance base to steal the vaccine. Unfortunately he was too late, and Solo died, but the vaccine was given to the other orphans. Solo's friend, who never contracted the virus despite never receiving the vaccine, attributed it to his friend's protection, and named himself "Duo" in honor of his fallen friend.
He appears only in the novelization of Endless Waltz, and is mentioned in Episode Zero.