2. 5 Seconds of Summer: 21 Under 21 (2014)

Miller Mobley
Calum Hood, Michael Clifford Luke Hemmings and Ashton Irwin of 5 Seconds of Summer photographed on June 29th at the Radisson Blu Hotel in Milan by Miller Mobley.

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Birthdates: Michael Clifford: November 20, 1995 (Age: 18); Luke Hemmings: July 16, 1996 (Age: 18); Calum Hood: January 25, 1996 (Age: 18); Ashton Irwin: July 7, 1994 (Age: 20)

Last Year’s Rank: N/A

Why They’re Hot: Some would say the boys of 5 Seconds of Summer are hot just because they have tattoos, play guitars, and wear sleeveless band tees. But those aren’t the only factors that have made the Australian quartet rise from relative unknowns to superstar status in less than a year. After gaining notoriety via YouTube, the band got its big break by opening for previous 21-Under-21 topper One Direction on its 2013 Take Me Home tour. These days, though, 5SOS is doing just fine on its own. The band boasted millions of twitter followers and rocked 2014’s Billboard Music Awards well before they even had an album to its name. 5SOS’s self-titled debut dropped June 27 and songs like “Amnesia” and “She Looks So Perfect” quickly surged on the Billboard Hot 100 (they peaked at no. 16 and no. 24, respectively). The group’s current tour wraps Nov. 16, but they’ll be back with a vengeance in 2015. Beginning May 4 of next year, the boys will embark on a worldwide arena tour that will hit North America, Australia, and over a dozen European nations. If the momentum keeps up, 5 Seconds of Summer have a good chance of sticking around much longer than their name implies.

21 Under 21's Next Class | Top 21 Songs by Under-21 Singers 


Billboard's 2014 21 Under 21 List