In the Legends' production of Romeo and Juliet, Romeo (Constantine) and Juliet (Zari) share a kiss at the very end of the balcony scene, but this kiss doesn't occur in the actual play.
Shakespeare says that he is having trouble figuring out how to end Romeo and Juliet, but the story (and the ending) did not originate with Shakespeare. It was first published as "The Tragedy of Romeus and Juliet" by Arthur Brooke in 1562, although the story predates its publication.