How did Shakespeare come up with the idea for the play Romeo and Juliet?

Although my heart would love to believe that the basis of Romeo and Juliet was presented in truth through the movie Shakespeare in Love, that is simply not the case.  I'm afraid the real story behind Romeo and Juliet is a lot less romantic in nature.  The basic story of two tragic lovers was taken from a poetic drama by another English contemporary of Shakespeare's named Arthur Brooke.  It was originally published in 1562 and again in 1587 under a new title:  The Tragically Historye of Romeus and Juliet.  In fact, Brooke didn't take the ideas from his own head either.  Brooke relied heavily upon a French version of the same story by Pierre Boaistua.  Ironically, though, it was Luigi Da Porto (undoubtedly from Italy) who set the story of the fated lovers in fair Verona of his own country.  Of course, their names were originally "Romeo" and "Guiletta," and that was way back in 1530.  However, the stories of feuding families go back even further than this.  Roman and Greek mythology is full of stories of that sort.