Who really is to blame for the final tragedy in Romeo and Juliet?

At the end of the play Romeo & Juliet, written by William Shakespeare, both of the protagonists, Romeo and Juliet die. But who really is to blame for the two lifeless bodies? The text will describe why the Friar Laurence, both of their families and Romeo & Juliet themself are responsible for their deaths, even though there are many more people who could be made responsible it.

Friar Laurence
Even if he had the best intentions to help Romeo and Juliet to get married and break feud between their two families, who have been enemies for centuries, he was the one who up with the idea, that would kill them both. After Romeo got banned out of the city, Juliet told the Friar that she is supposed to marry Paris, the Prince's cousin, the Friar came up with the idea to make it look like she died in her sleep with a potion that will make her fall asleep for 42 hours. While Romeo waits in Mantua, his servant comes and tells him that he saw Juliet being placed in the Capulet tomb. Romeo is not ready to believe she is dead. He buys a poison that will kill him instantly and leaves to see if her death is truth. In the meantime, Friar Laurence sends a letter to Romeo to explain the whole situation, but it is too late. When Romeo gets to the tomb, he encounters Paris. The two fight and Romeo kills Paris. He enters the tomb and sees Juliet. Thinking she is dead he drinks the poison and dies instantly.
The Friar races to the tomb, but he is too late and sees Romeo dead on the floor beside Juliet. She awakens to find Romeo dead beside her. Juliet takes Romeo’s dagger and stabs herself.
If the Friar wouldn't have come up with the idea of making it look like Juliet died or marrying Romeo and Juliet that fast after they met each other, they might still be alive at the end of the play.

The families
The book begins with explaining that the feud between the two families is going on since centuries, what indicates, that this feud is pretty important. And it is, just this feud is the reason why all the characters that died in the play died. Because of the hate between the two families Tybalt wants a swordfight between him and Romeo, but Romeo refuses to fight. In the end Mercutio draws his sword against Tybalt and gets killed. Romeo gets so enraged by Mercutio's death that he challenges Tybalt and kills him. Because Romeo killed Tybalt, but only because Tybalt killed Mercutio, he gets bannished from the city Verona. His mother, Lady Montague, kills herself because of the misery about Romeo getting banished from Verona. After Romeo saw the Juliet who was meant to look like she is dead, he took a poison and died immediately. Juliet stabbed herself with Romeo's dagger after she saw him laying dead beside her. All those deaths belong to the hate between the two families and could have been saved, if Lord Capulet and Lord Montague would have stopped the feud between their families. Because I am sure that they did not even know the reason of the hate, because it was never mentioned in the book. They just did what their parents did, who did what their parents did and so on.
So in the end everything would be good if the families would not have hated each other.

Romeo & Juliet
When Romeo attended Capulet's party to compare Rosaline's beauty with all the other women's on the party, like Mercutio told him to do, and fell in love with Juliet he could have resisted his