Mardian was one of Cleopatra's childhood friends. He was a eunuch, who went onto to becomes her personal advisor. Cleopatra never took his loyalty for granted, and she was quick to point out how fortunate she was to be surrounded by people such as Mardian. It was Mardian who first suggested that Cleopatra should marry after young Ptolemy's death.
The Memoirs of Cleopatra: A Novel