Kavan,
I believed narrow jaws are less caused by genetic than our diet in our childhood. It's because of mashed potatoes, chopped steak, yogourt that our jaws did not developped well.
For aesthetical and health reason (balance of the squelettal, performance in sport, breathing) we do need large jaws. There is no exception.
The same thing can be said about people with a long face. It is more because there were (are) mouth breather than genetic that they have this issue.
Environnmental factors such as oral posture are more important.
In my family, nobody have needed orthodontics except me. Why ? Because I used to suckle my thongue for years. And I was the only one doing it. Maybe I was insecure