Depends. Did something happen to his hair before like get contaminated with something? If no, then it could be hereditary. You can change anything seriously even if it is hereditary. Hereditary + Environment = What you are now. So, you can go to your hair dresser and ask for some liquid for growing hair (I am pretty sure they will have some). If it still doesn't work, consult a doctor. Discover what's wrong and then work on what's wrong. Good Luck.