You are welcome to have somebody along, but they will have to entertain themselves otherwise and elsewhere during the photo session.
See also: whilst you wait
During the session there is only you and me and possibly a makeup artist - unless, of course, it is a photo session for you with your partner.
I feel that it is not right to accommodate spectators: A photo session is like a conversation between two people, the photo-grapher and his client. Other people tend to get in the way, distract and disturb the creative flow.
Professional models are used to performing naturally with many other people present. People who are not used to standing in front of the camera every day are too easily distracted and inhibited in the presence of company.
If you commission me to photograph a baby or child, then of course a parent must be present.
Teenagers can be very inhibited in the presence of their parents. A responsible adult needs to be on hand but it may be preferable for them to wait in another room.
