Why is it called Cleopatra's Second Husband?

As I understand it, the title is a reference to the common portrayal of Mark Antony as Cleopatra's plaything. Zack is Cleopatra and Robert is Mark Antony. Technically, this should be called "Cleopatra's Third Husband" since Cleopatra VII had been married to her brothers Ptolemy XIII and Ptolemy XIV before Mark Antony.