A portrait reflects the close relationship between photographer (or painter) and subject.
I cannot imagine ever portraying someone I do not know. Before portraying someone, I personally prefer sharing a meal with them, because that is when we truly relax, break free from our socially constructed roles and really get to know each other. I have always believed that, in order to achieve a good portrait, people must feel at ease, which is why I prefer portraying adults in their working environment or living room, since there they are familiar with their surroundings and can relax and not “pose”. Similarly, when I am asked to take a picture of a child I observe them while they play with their friends, maybe taking more time than it would be necessary, because I do not like it when children stare at the camera with a fake smile like some kind of stuffed animal.