OK If you have to discuss the proposition, then you have to have points on both sides.If they were victims of fate, then they could do nothing to prevent what happened. If they were not, then the final outcome was a result of the choices they had made.
For: enmity of families from before they were born. Romeo's philandering nature.
Against: decision to take sleeping drug. Decision to defy parents' wishes.Plan too complicated? Too many things that could go wrong?
Hope this helps