Funny Faces

Does anyone know why my son will smile for the camera when he is alone in a picture but not when there are other people involved? Below is an example of my dilemma. This is my friend Carly from high school (also a bridesmaid in our wedding and namesake of the family dog) with her new son Peyton back in KC. Tommy wants nothing to do with smiling in this picture or other recent family shots. At least Carly and Peyton look good!