In his 1562 narrative poem The Tragical History of Romeus and Juliet , Arthur Brooke translated Boaistuau faithfully but adjusted it to reflect parts of Chaucer's Troilus and Criseyde .  There was a trend among writers and playwrights to publish works based on Italian novelles —Italian tales were very popular among theatre-goers—and Shakespeare may well have been familiar with William Painter 's 1567 collection of Italian tales titled Palace of Pleasure .  This collection included a version in prose of the Romeo and Juliet story named "The goodly History of the true and constant love of Romeo and Juliett" . Shakespeare took advantage of this popularity: The Merchant of Venice , Much Ado About Nothing , All's Well That Ends Well , Measure for Measure , and Romeo and Juliet are all from Italian novelle . Romeo and Juliet is a dramatisation of Brooke's translation, and Shakespeare follows the poem closely but adds extra detail to both major and minor characters (in particular the Nurse and Mercutio).   
The suddenness of Romeo and Juliet’s love, the circumstances in which they are a part—that of belonging to feuding families, and their extreme youth all contribute to the feeling that this is a temporary relationship. Romeo and Juliet’s concern is temporarily keeping their marriage secret—hoping to eventually fulfill the role of peacemakers.
An example of Romeo and Juliet’s concern with who they are is illustrated in Juliet’s balcony speech:
O Romeo, Romeo, wherefore art thou Romeo?
Deny thy father and refuse thy name!
Or, if thou wilt not, be but sworn my love,
And I’ll no longer be a Capulet. (-39)
‘Tis but thy name that is my enemy;
Thou art thyself, though not a Montague.
What’s a Montague? . . What’s in a name?
That which we call a rose
By any other word would smell as sweet . . (-43/46-47)