Sister or symbol?

Heard a Emilio Bañuelos in an interview by The Candid Frame podcast the other day (actual interview took place a couple of years ago). He said his greatest challenge in teaching his photography students was to get them to take pictures of friends and family that represent something more than a specific narrow "this is my friend" point of view. They are challenged to take those pix so they speak to everyone that sees them...not just the photographer. Sorta like a picture of "Mary" my mom should convey "motherhood" to everyone else. Been thinking of ways to creatively convey this concept.