Cleopatra had known Mark Antony since she was a teenage girl. This was during her father's reign because Mark had helped Ptolemy (her dad) to get back on his throne. She had also met him countless of times during her visit in Rome. He was known to be a handsome man but Cleo never took notice in him, maybe because of their lack of mutual interest: she liked books, learning, science, etc whereas he liked wine and women. That, or maybe it's because he wasn't powerful enough.