1
general::
A favorite, a person who is given special treatment. For example, Today the attorney general is the governor's fair-haired boy. This term alludes to the preference of blond ("fair") hair over dark hair. [Late 1800s]
American Heritage Idioms
2
general::
Phrase(s): fair-haired boy
Fig. a favored person. (Not necessarily young or a boy.) • The teacher’s fair-haired boy always does well on tests. • The supervisor’s son was the fair-haired boy on the construction site.
McGrawhill's American Idioms And Phrasal Verbs