In the 90s, the Backstreet Boys were on top of the world. They sold over 100 million records across the globe, had hearts throbbing in every country, and were the type of boy band that would span decades.

RELATED: 15 Pop Culture Icons From The 90s Who Have Managed To Stay Relevant Today

But no matter how much you loved BSB when they first became famous, there are probably some things you don't know about them. After all, the guys tended to keep their private lives private while performing as the Backstreet Boys, even when some of the members were having personal issues. From legal strife to falling outs between group members, here are 10 things most fans don't know about BSB.

20 AJ McLean Was The First Member

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While some boy bands get started because the members are friends first, that wasn't the case with BSB. In fact, all the guys responded to casting calls from Lou Pearlman, the now-disgraced (and deceased) former manager of NSYNC, Backstreet Boys, and numerous other boy bands.

AJ McLean was the first to sign up with BSB, after auditioning for his role. The other four guys — Kevin Richardson, Nick Carter, Brian Littrell, and Howie Dorough — came after. Unfortunately, though Ryan Gosling could have been a member, he opted out.

18 The Band Was Big In Europe First

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When the Backstreet Boys first got together, they weren't huge in the U.S. Wikipedia notes that their first concert was at SeaWorld Orlando, with a handful of other small gigs to follow. What really spurred them to fame was the success of their first song in Europe.

"We've Got It Goin' On" wasn't huge in the U.S., despite what 90s kids later thought, but it did top charts in Europe. Later, NSYNC would follow this same model of success under Lou Pearlman's guidance.

16 Brian Littrell Had Heart Surgery On Tour

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Most fans never heard about Brian Littrell's heart issues, at least not until many years after his open-heart surgeries. In 2008, ABC News reported that Brian's son Baylee has Kawasaki syndrome, a condition that involves swollen blood vessels.

Brian himself was born with heart problems. At age five, he had surgery to correct a heart murmur. Then, mid-tour with BSB in 1998, he had a second surgery to repair a hole in his heart. Unfortunately, heart problems might be hereditary in the Littrell family.

14 Orlando, FL Had An Official BSB Day

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BSB may not have reached the level of 90s meme fame that Justin Timberlake's hair did, but the mayor of Orlando, Florida, did give the Backstreet Boys the key to the city. He also declared the day Backstreet Boys Day, something that would have delighted fans had they known about it at the time.

October 7th was the official BSB day, noted Orlando Sentinel, and it was a result of the boys raising money for tornado relief in the Orlando area. The headlining act was responsible for contributing over $250K to the cause.

12 Nick Spurred The Band's First Hiatus

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Remember when Nick's little brother Aaron became famous? While things later went downhill for Aaron Carter, it seemed that Nick also wanted his chance at a solo career. At one point, Nick left the band, leaving the other four members to flounder a bit without him.

At the same time, JIVE records apparently promoted Nick's album to the detriment of BSB as a whole. That meant the guys would go to court (again) with a lawsuit trying to recoup their losses.