2.) Choose the lasso tool (L) and select the sons face. Move it over top of the fathers face. Go to Edit > Transform > Flip Horizontal. As I'm sure you guessed, this flips the sons face horizontally to better match with his fathers face.
3.) With the sons face selected hit "CTRL + T" to bring up the transform box around the image. begin to adjust the size of the face, twist the image if need be.