20. One Direction
The most successful boy band to date, the five-member band One Direction had an incredible career. Even though the group has dissipated, the band saw multiple number one Billboard hits and millions of record sales. They also managed to sell out arenas and theaters across the world during the peak of their career. Even now as individual artists, we see their fan bases predominantly filled with grown adult fans that once followed One Direction religiously.
Image Source: Anthony Harvey/Getty Images