At the very start of the parlt in the the prolouge it says that  both the star crossed lovers fate is sealed and they will die. The star crossed lovers being Romeo and Juliet, but also in the play there a rare many clues said by the characters talking about there future. Romeo says in the play that his consequence is left hanging in the stars, which means that his fate is in the hands of God. He also says that somethinbabas will happen, but he only says that about the party that night so that time he wasnt talking about his future. Shakespeare uses dramatic irony which is when we the audience know something that the characters don’t in this case  we know that Romeo and Juliet are going to die.