Remembering faces requires several different brain regions on both side of the brain, and all children need to mature in their recognition of faces. The anatomical complexity of facial recognition and memory means that there are many different ways these cognitive tasks can be affected. This means it is developmentally normal for young children to not be as quick as adult distinguishing faces, and problems remembering or recognizing faces can occur from very different causes.
The right prefrontal area here is important for remembering faces (nonverbal), but the left prefrontal area is seems to be necessary for integrating and making meaning of both the emotional and visual aspects of faces.
Memory for Faces
Post: Developmental Changes in Face Perception