When Friar Lawrence married Romeo and Juliet he gave them hope to be together in hope of stopping the feud between families. What he didn't realize is that the feud would only end after both Romeo and Juliet where dead. Then when Juliet comes to him for help he gives her the potion which eventually leads to Romeo committing suicide after believing Juliet was dead. Shortly after this causes Juliet to follow Romeo's actions. If Friar Lawrence hadn't married them than there was a possibility neither of them would have died