And many people in the nobility of Florence had the same first name and same last name. If your brother died, you might well name your next son after him. Boys were typically named after grandfathers, so cousins wound up with the same names. It isn't easy keeping track.
While I have done my best to untangle the information I found, and while I have held true to undisputed historical data, I have looked at controversial points as offering freedom to make those choices that would move my tale in interesting directions. I have also taken liberties with shaping personal lives, always with an eye toward what was possible, and sometimes statistically probable, for the society as a whole.
Over and over, I returned to the portrait itself. Like the Leonardo of this story, I tried to glean information from the mysterious woman's eyes and her jawline and, most of all, her smile.