Is Nancy drew and hardy boys fantasy books?

Both series were created by the Stratemeyer Syndicate, a children's book packager which also created the the Bobbsey Twins, Rover Boys, and Tom Swift series. The printed authors for all of these series are pseudonyms (fake names used by many authors).

There have been two ND/HB crossover series: The Nancy Drew and Hardy Boys SuperMystery series produced 36 books from 1988 to 1998, and the Nancy Drew and the Hardy Boys Super Mystery series, which has produced four books since 2007.