It is never revealed why the Montagues and Capulets, the two feuding families in William Shakespeare's "Romeo and Juliet," become enemies. In the first four lines of the prologue, it is explained that "Two households, both alike in dignity,/ In fair Verona, where we lay our scene,/ From ancient grudge break to new mutiny,/ Where civil blood makes civil hands unclean."
In other words, two well-respected families in the city of Verona have harbored grudges for many years. No one seems to know or talk about what started the feud. Seen individually, both families appear to be friendly, hospitable people who love their children. The two families, however, despise one another, even the younger members who were not around when the feud started and the servants who are not related to either family. In the play, the Capulets are having a party, and, of course, the Montagues are not invited. When Romeo, a Montague, crashes the Capulet masquerade party and is recognized by his voice, the feud is on again. In the meantime, Romeo and Juliet, a Capulet, have fallen in love and want to marry. The Friar thinks their marriage has the potential to end the feud, and he performs the ceremony. During the course of the few days covered by the play, members of both houses die defending family honor, and Romeo and Juliet themselves die. With their deaths, the feud finally ends.