"Death mark'd love" clearly states that death is a big part of the two young ones ends. Towards the end of the play, it becomes evident that death has a heavy upper hand in Romeo and Juliet's relationship, one faking suicide to be with her lover, and the other killing himself when he sees that his lover is "dead". Star-cross'd lovers indicates that their paths aren't the best, yet they're set out to make it worth it. Since their families are in a constant declared war, the two shouldn't be in love, though they are.
