Noble hearted, loyal, and—at the beginning of the play—uninterested in romance, Valentine falls in love with Sylvia, daughter of the Duke of Milan and Valentine's host. Their feelings are mutual, and the two plan to elope because the Duke has other ideas about a suitable marriage for Sylvia. When his plans are thwarted and he is banished, Valentine becomes an outlaw leader. Valentine's admirable principles and courage finally impress the Duke, who reconsiders his thoughts about Valentine marrying Sylvia.
Proteus is the other Veronese "gentleman" of the play's title. When his best friend Valentine goes off to Milan, Proteus stays in Verona and woos Julia. When his father sends him to Milan, too, Proteus falls in love with Sylvia, abandoning Julia and deceiving Valentine. Like the shapeshifting Greek sea god for whom he is named, Proteus is inconstant. He has no permanent loyalties or affections but casually sells out his friend and ignores his promises to advance his own goals.
In love with Proteus, Julia first expresses indecision about whether to accept Proteus's love letters. She makes up her mind just as Proteus is about to depart for Milan, and the two exchange rings as love tokens. Not content to wait at home for Proteus's return, Julia defies convention and travels to Milan disguised as a page to be with Proteus, who is now trying to court Sylvia. Completely loyal to the caddish Proteus, who is courting another woman, Julia forgives him when he comes to his senses at the play's end.
As the daughter of the Duke of Milan Sylvia is expected to marry the man her father chooses rather than Valentine, the one she loves. She recoils at the idea of marrying the rich but inelegant Thurio, the suitor preferred by the Duke. Nor is she interested in the deceitful Proteus. Showing determination and defiance, she runs away from Milan to seek her exiled lover after their plans to elope are thwarted.
The Duke of Milan is, in many ways, the typical father in Shakespearean comedies. He demands obedience from his child and wishes her to marry for political and financial reasons, not for love. To prevent his daughter Sylvia from becoming seriously involved with Valentine, he locks her up at night in an inaccessible room. The Duke is taken in by Proteus's schemes and lies, which serve only to advance Proteus's desire to court Sylvia. However, sufficiently impressed by Valentine's noble qualities, the Duke finally gives his consent for Valentine and Sylvia to marry.
Thurio is a rich but slow-witted and shallow Milanese nobleman who vies for Sylvia's affections. His vast wealth makes him the preferred suitor in the Duke's eyes, but Sylvia dislikes him. Undaunted, he enlists Proteus's help in wooing Sylvia with poetry and music, but these attempts also fail to make an impression. At the end of the play, when he is revealed as a coward, Thurio changes his mind and relinquishes his "claim" to Sylvia.