How do the parents’ actions advance the plot?

Pyramus and Thisbe's parents advance the plot because of their negativity. The two have known each other all of their lives, and their friendship, which turns to love, has nothing to do with grudges or hatred. In truth, the fact that the parents forbid their relationship and disapprove of their desire to marry makes it all the more attractive. The couple's desire to be married in spite of their parents' wishes, however, leads them into danger.... and in the end, their deaths.