For some reason the camera portrait has been accorded status as impartial and free of bias, although anyone who practices this art knows better. Portraiture is more than likeness, more than family record. Portraiture is linked to human issues now taking their places in our conscious self-knowledge as a civilization. To be able to look into the eyes of a forebear and feel the link. Right into the eyes, and to see them looking back at you.
Genetic connection seems to heighten the impact.
At this late date many jurisdictions are finally passing legislation to guarantee adopted people access to records necessary to finding their birth parents. Adoptees have demanded this basic right for generations. All humans want to know their roots. The impact of a portrait of one's never-known parent is incalculable. Baby pictures are another good example.