Both of them change and mature throughout the play. We get to have an in-depth understanding about these characters and two or more sides of their personality are seen.
Romeo is a tragic and romantic figure. He begins as a young man entangled in his own superficial notions of love. His interest in Rosaline is passive and non reciprocal in comparison to the more complex and active relationship he develops with Juliet. He’s the young son of the Montague family, around 16 years old. He is very handsome, intelligent, romantic and impulsive. He’s life is ruled by love. He was in love with Rosaline, but then goes into depression when she does not agree to his wishes. This is when he sees Juliet and falls in love at first sight. His feelings always seem to be at extremes.
After marrying, Romeo's relationship with Juliet becomes even complex and involves many factors other than themselves. An important moment occurs when Romeo encounters his old enemy Tybalt, who he is now related to by marriage. He tries to avoid violence as well, but if he wants revenge he will get it. Romeo eventually responds to Tybalt's challenge and kills him in a fight after Tybalt killed Mercutio. He's very good friends with Mercutio, and Benvolio is his cousin. Unfortunately, for this murder, Romeo is banished to Mantua and separated from his new bride. When he receives word, mistakenly, that Juliet is dead; Romeo is devastated and immediately decides to join her. He goes to Juliet's grave where he meets Paris, and kills him. After that Romeo finds Juliet's seemingly lifeless body in the tomb and says, "I will stay with thee and never from this palace of dim night. Depart again". With that, Romeo kills himself by drinking poison. Committing suicide is Romeo's final and most profound act in his pursuit of Juliet.
Juliet is the beautiful and only daughter of the Capulets. She’s still a young girl when the play begins, not yet 14, as we know by the Nurse "Even or odd, of...