In Act 3, scene 1 of Romeo and Juliet, Romeo is faced with several moral questions that relate to the themes of the play.
On the one hand, Romeo does not want to fight against Tybalt because he is a Capulet. As Romeo married Juliet in secret, he considers Tybalt his family now. This touches on the themes of family and love. However, Romeo wants to defend Mercutio, and later on avenge his death. This addresses the subject of loyalty. Finally, Romeo feels that his love for Juliet has made him "effeminate" and unable to fight. This addresses the themes of honour and masculinity. It also discusses the effects of love.
Romeo kills Tybalt right after he marries Juliet in Act III. He is now family to Tybalt and does not want to fight him, but he can't tell anyone why. Romeo wasn't ever much of a fighter in the first place, and, due to the Prince's ultimatum from Act I, there are many reasons why Romeo wouldn't want to fight Tybalt. Still, Mercutio engages Tybalt in a duel after Tybalt hurls insult after insult at Romeo....