Firstly, Peter, the Capulet’s servant. He is illiterate, and he had been given the job of inviting friends of the Capulets to their feast. He can’t read the names of the people he’s meant to invite, so he asks Romeo for help. He is so grateful to Romeo, that he invites him to the feast without knowing that he is a Montague.
Mercutio is at fault because if he hadn’t forced Romeo to go to the Capulets feast, Romeo would never have met Juliet. Also, later on in the story, Mercutio gets into a fight with Tybalt. Mercutio is killed, and Romeo kills Tybalt to avenge his friend’s death.
The Nurse is responsible because she encouraged Juliet, by delivering the couple’s messages and even helped arrange the secret wedding. Furthermore, she advised Juliet to marry Paris when she knew Juliet was already married to Romeo by saying in Act 3, scene 5
“I think you are happy in this second match,
For it excels your first: or if it did not,
Your first is dead; or ‘twere as good he were”.
Tybalt started the fight between him and Mercutio, and throughout the play he keeps reminding everyone of the feud between the families.
The Prince should have stopped the feud between the families sooner. He threatened to execute the heads of the families if there was any further disturbance to Verona, but he didn’t stick to his warning. It wasn’t fair to banish Romeo for the fight that had been started by Tybalt either.
Of all the people so far, Friar Lawrence is most at fault. He agreed to marry Romeo and Juliet, he gave Juliet the sleeping drug and he didn’t get the message to Romeo.
Lord and Lady Capulet and Lord and Lady Montague are to blame because at heads of the families they could have stopped the fighting. Also, the Capulets should have listened to Juliet when she said she didn’t want to marry Paris, and the Montagues should have been more understanding towards Romeo. If they had, he might have felt that he could tell them about Juliet.
Lastly, Romeo and Juliet. Romeo shouldn’t have rushed into marriage and he shouldn’t have rushed back to Verona after hearing of Juliet’s death. He didn’t stop to think of the consequences, like his death for returning illegally to Verona. He acted violently and without thinking towards to Tybalt.
Juliet also shouldn’t have been so hasty about marriage.
In conclusion, the people who were most to blame for Romeo and Juliet’s deaths were Romeo and Juliet. They should have acted more responsibly. Being in love is no excuse for being stupid.