Friar Lawrence secretly married Romeo and Juliet. Even though Friar Lawrence knew they wouldn't be able to tell anyone because a Montague and a Capulet cannot be married, but he still married them anyway. Although he had doubts he still married them because Romeo asked him too and he was just being a friend. There were only four people in the book that knew about them getting married. In act 2 scene 4 when Romeo is asking Friar Lawrence to marry him and Juliet Friar says " These violent delights have violent ends...." So he is warning Romeo that something might happen.