How do the characters of Romeo and Juliet develop throughout the play?

Both Romeo and Juliet mature during the play. In Act I, scene i, Romeo is in love with Rosaline without hope, for she has sworn to remain chaste and single. He is moody and depressed, and in the next scene, when Benvolio suggests he attend the Capulets' ball in order to find a new love, he only agrees so that he will have the opportunity of gazing on Rosaline. As soon as he sees Juliet, however, he forgets his infatuation with Rosaline as he truly falls in love.

Romeo's love for Juliet helps him see beyond the brawl between his family and the Capulets so that in III.i, he tries to stop the fight between Tybalt and Mercutio and even steps between them. He only fights Tybalt after Mercutio has been killed and he feels he must revenge his friend's death. Again, in Act V, he immediately makes plans when he hears of Juliet's supposed death, and when he kills Paris in his attempt to get to Juliet, he honors Paris's wish of being laid next to Juliet in death.

In the beginning of the play Juliet is the model young and innocent daughter. When asked if she would like to be married, she replies, "It is an honor that I dream not of." But after she marries Romeo, Juliet matures beyond her fourteen years and assumes the responsibilities of a wife. She gives up her dependency on her nurse and risks pain and death to remain true to Romeo.