Posca is a fictional character as far as I can discern. He certainly seems much too cynical to be the marrying type. Not sure how a married Posca will go over in the series. I do enjoy his sardonic wit. For example:

Posca brings a new list of Romans marked for proscription

Posca: "More names from Mark Anthony."

Octavian: "More?"

Posca: "Anthony has many enemies. It takes time to remember them all."