Who do you prefer to be the narrator in stories? With mother and son, do you want the mother or son's point of view? With father and daughter, do you want the father or daughter's point of view?
In other stories, do you like to see the character with the most power be first person? For example, with aunts and nephews, who should be telling the story?
I ask this since I noticed that women like my cuckold stories more if the wife tells the story.