Answer: The Prologue points out that Romeo and Juliet have fate against them. It says that their love is "death-marked," and they have no control over what happens. It is their misfortune that leads to the sorrowful and tragic ending of the play.
Relative pronouns is your answer. Relative Pronoun: A pronoun that introduces relative clauses and the element modified. Relative Clause: An adjective clause introduced by a pronoun. Hope this helps! :)