There are several people that could be blamed for the deaths of these two young people, including their parents, by keeping the feud between the two families going. Mercutio can be blamed, to some degree. He was the one who got Romeo to go to the ball. When Mercutio was killed, Romeo avenged his death, and ended up having to leave Verona instead of staying with Juliet.
However, one of the characters who is most to blame could be Friar Laurence. Friar Laurence was the wise adviser to Romeo and Juliet. He kept their secret and helped them be together. He was the one who married the two, hoping that the marriage would cause an end to the feuding. He was the one who came up with the idea of giving Juliet the potion to put her in a coma-like state for 42 hours. He wrote a letter to Romeo, explaining the plan, but the letter never reached Romeo. After the two of them died, the Friar left, so his plan was never found out. Friar Laurence, being a man of God, could have gone to the families and told them that the feuding had to end. They may have listened to him. They trusted him. The nurse is another one who can be blamed, as well. She was Juliet's trusted friend. She sent letters to Romeo for Juliet. She helped Juliet when she was going to marry Romeo. When it was told that Romeo was gone, the nurse agreed that Juliet should marry Paris. She didn't stand up for Juliet's love for Romeo.
Some of the blame also has to be placed on the shoulders of Romeo and Juliet. They were young and reckless. Instead of trying to figure out a way to make their relationship work, they both killed themselves. They have to be held responsible to some extent. This beautiful tragedy has many people that can be blamed. Two young people, who truly loved each other, felt that they had no other choice than to do what they did. The people in their lives could have prevented all of this. That is the true tragedy.
Perhaps it is also worth mentioning that in Act V, Scene 3, Friar Laurence's fear of the guards finding him in the tomb directly leads to the death of Juliet; for, had he remained with Juliet, she would not have been able to kill herself.
Friar Laurence. ....For the watch is coming. / Come, go, good Juliet, I dare no longer stay.
Juliet. Go, get thee hence, for I will not away.
[Exit Friar Laurence]
If, then, there is but one culprit who must be chosen, Friar Laurence is the most culpable as he secretly marries the lovers, he hides Romeo, and he provides Juliet with the sleeping potion; moreover, he leaves the emotionally vulnerable Juliet when he could have forced her out of the tomb with him.
His failure to speak with the parents and seek to ameliorate their hatred and his other actions go completely against his religious vows as well as being unconscionable.
Many people could be blamed for the death of Romeo and Juliet. Ultimately, I believe that Romeo and Juliet themselves are the people to blame. They were very young and they broke the rules. They killed themselves because they did not think about the consequences of their actions and the whole thing could have been avoided. Of course their parents could have some blame for keeping them apart because of family differences. Friar Laurence could have some blame for keeping secrets. The nurse could be blamed for keeping Juliet's secrets and knowing she was not sick. However, in my opinion, the overall blame should be placed on Romeo and Juliet.
There are many people in the play that contributes to Romeo and Juliet's death. I would state that their death was mostly cause by their families. As the readers know, the Capulets and Montagues were not on good terms with each other. Unfortunatly though, Romeo and Juliet fell in love with each other regardless if they are from opposing families. Because of these families' bad relationship, Romeo and Juliet was forced to marry in secret instead of publiciting it. These two lovers could have been straight-forward to their parents about their marriage, but they chose not to.
The friar is also guilty to these lovers' death, but he only thought that this relationship between Romeo and Juliet be the cure to their families' grudge for each other. It just happen to be that his plan did not work and the lovers took suicidal action on their own will. Yes, the friar seems to be more of the culprit, but the cause of making this relationship undergo complication is because of the Capulets and Montagues. Both of them let their anger get ahead of themselves and let the next generation to suffer what they really have nothing to do with. Overall, I could have write more, but I would like it make it brief that Romeo and Juliet died because of their forbidden love, which was cause by their families.
There are a number of people that could be blamed for the death of Romeo and Juliet. However, in the end, it is their decisions and actions that eventually cause their own deaths. Romeo and Juliet had many opportunities to come out to their families about their marriage. When Juliet's father insisted that Juliet marry Paris, she could have been honest and told him why she could not marry Paris; instead, she beats around the bush and asks to delay the marriage instead. Romeo, when he saw Juliet in the tomb, did not have to take the potion. He could have dealt with his grief and tried to move in, which would have given the play and entirely different end because Juliet was not dead. Romeo is such a dramatic love-sick character, however, that it would have been completely out of character for him to live without Juliet.
An argument could easily be made for many of the characters in Romeo and Juliet, but one of the strongest arguments points towards the families. They chose their hatred of each other over their own children's happiness and, ultimately, were left with nothing.
In my opinion, I believe that Tybalt is the one to blame.