The Opportunity is a Caroline era stage play, a comedy written by James Shirley, published in 1640.
Shirley relied on El Castigo del Penséque by Tirso de Molina as his source for the plot of his play.
During the Interregnum when the theatres were closed, material from The Opportunity was extracted and performed as a droll called The Price of Conceit, published in The Wits in 1672.
Borgia also has a beautiful sister called Cornelia, a waiting woman to the Duchess—with whom Aurelio quickly falls in love.
The Duchess, too, is enamored of Borgia/Aurelio, to the displeasure of her courtiers; and she is a beautiful and desirable woman who can make her husband a duke.
Aurelio, thinking that he will lose both women, asserts his true identity: he tells "Cornelia" that he is not her brother, and asks her to love him for himself.
Next morning, the Duchess tells Aurelio that she will help him to any Urbinese bride he fancies, even "the proudest, greatest in our duchy, without all limitations."