This photo, titled Indian Chief, is one of his works. This has an amazing composition, with just enough negative and positive space to draw the eye in. His face is gently shadowed, as opposed to harsh lights and shadows, and it seems as though everything has a shadow and a highlight- nothing is left out.
This one directs the eye to the right and down, since they are both looking that way. It gives a sense of completeness, since your eyes travel across theirs'. The difference between the dark clothes on the lady and the white bundle the baby is it gives it a nice contrast and balance.
Since they are looking away from the camera, it again draws the eye around the photo, and also gives it a bit of a more candid and personal feeling; They are centered in the photo, giving it a nice composition.