What is the irony of the Prince's message to the parents at the end of Romeo and Juliet?

That it came true? They were doomed star crossed lovers... Romeo: I fear, too early: for my mind misgives

Some consequence yet hanging in the stars

Shall bitterly begin his fearful date

With this night's revels and expire the term

Of a despised life closed in my breast

By some vile forfeit of untimely death.

But He, that hath the steerage of my course,

Direct my sail! On, lusty gentlemen.