Two hours before taking the stage in Minneapolis for a March Madness Music Series concert, the Jonas Brothers meet in Nick’s hotel room for some preshow brother time -- and, OK, to get their hair done. It’s early April, and as Kevin waits his turn, he pulls out his phone. “Check this out,” he says, bouncing up from the couch to show off a Google Maps image. A Twitter user has traced the line of people waiting to get into the show, equivalent to almost six city blocks. “Isn’t that crazy?”

Fans began lining up at midnight, camping out in their Jonas Brothers tour T-shirts from 2008 and blasting fan favorites like “Year 3000.” This kind of dedication has been par for the course since the sibling trio debuted in 2006 -- only now those fans are adults whose steadfastness helped “Sucker,” the group’s first single in nearly six years, debut at No. 1 on the Billboard Hot 100 in March. (They’ll perform it at the Billboard Music Awards on May 1, airing live from Las Vegas on NBC.) It’s a feat the brothers never accomplished in their late-2000s heyday, despite selling out arenas around the world and topping the Billboard 200 twice. It’s also a stamp of grown-up pop stardom for a band that never got to age into it, thanks to an abrupt split in 2013 due to general burnout and conflicts over the group’s direction.

Tonight’s show at the 8,400-capacity Armory is the largest concert that the brothers -- Kevin, 31; Joe, 29; and Nick, 26 -- have played since announcing their reunion on social media on Feb. 28. With only two new tracks to play -- “Cool,” the witty follow-up to “Sucker,” debuted at No. 27 on the Hot 100 earlier in April -- the brothers’ 19-song setlist shows they’re more than happy to strut down memory lane. But when Kevin asks, “How many of you haven’t been to a Jonas Brothers show before?,” roughly three-quarters of the audience raise their hands. The group’s original fans still scream like prepubescent tweens, but now they’re joined by actual prepubescent tweens. (You don’t debut atop the Hot 100 without the youth stanning your song; “Sucker” had 151.3 million U.S. streams through April 18, according to Nielsen Music.)

“They’re the kind of band that’s bigger than anybody realized, and had more fans than anybody realized,” says Monte Lipman, founder/CEO of Republic Records, the act’s current label.

That there are so many recent Jonas Brothers converts shouldn’t be a surprise. During the band’s hiatus, Nick launched a solo career that amplified his sex appeal with smoldering pop-R&B cuts like 2014’s “Jealous.” (“When Did Nick Jonas Get Hot?” read one representative headline from that year.) Joe started the unabashedly wacky pop-rock group DNCE, whose funky “Cake by the Ocean” was inescapable in early 2016 and, like “Jealous,” reached the top 10 on the Hot 100. Kevin, meanwhile, stepped away from music to start a real estate development company and focus on his family, wife Danielle and daughters Alena, now 5, and Valentina, 2.

The Jonas brand has benefited immeasurably from the brothers’ love lives: In addition to Danielle -- who co-starred with Kevin in the reality show Married to Jonas, which aired on E! in 2012 and 2013 -- there’s Nick’s headline-making marriage to Quantico actress Priyanka Chopra and Joe’s widely adored relationship with fiancée and Game of Thrones star Sophie Turner. The night before the Minneapolis show, after a surprise set at a favorite bar near Penn State, the “J Sisters” -- as Danielle, Chopra and Turner call themselves -- poured drinks and body shots for the crowd, lighting up social media in the process. (“They burned that place down,” says Kevin.)

Yet for all the fame that the Jonas Brothers banked individually, their return is a notable victory for boy bands: Outside of K-pop, no recent groups have sparked One Direction levels of pandemonium. (The Backstreet Boys are releasing new music, but their main audience comprises nostalgic elder-millennial fans with enough disposable income for tickets and meet-and-greets.)

The Jonas Brothers are making pure pop music at a time when rap dominates and the biggest “pop” stars -- Billie Eilish, Ariana Grande -- are making intensely personal music influenced by alternative and hip-hop. Though they’ve traded their famed purity rings for louche chest hair, what’s striking about the brothers is just how little they’ve changed: They’re earnest, family-oriented, clean-cut, commercially savvy hitmakers who just want to have a good time. And there is, apparently, an underserved audience for that.

Still, they’ve come a long way. In 2013, Joe remembers, “we all wanted to create something on our own and were just trying to force it into what was going on. We were going through the motions, without the heart of it.” Their disagreements took a toll on more than just their music: “The way we communicated to each other wasn’t healthy anymore.”

Sitting in the hotel room, they appear to be in a much better place, though light-hearted jabs still fly. After a trailer for Seth Rogen and Charlize Theron’s upcoming film, Long Shot, comes on the TV, Kevin says, “That’s like the plot of that Hugh Grant and Julia Roberts movie -- Notting Hill?” Nick snaps back, “Uh, no, that’s Love Actually.” (Later, they decide they’re both right.) When Joe walks in sporting an orange flip-sequined jacket, Nick runs his hand over it, and Joe jokes, “Did I say you could touch me?”

To hear the band tell it, this ease didn’t come, well, easy. It’s the result of many hourslong conversations required after years of bottling up their feelings. Getting to a place where they could release a new album -- their fifth, Happiness Begins, will arrive June 7 -- wasn’t simply a matter of aligning schedules. They had to renew their relationship as siblings and as musicians.

Yet their story would make for a third-rate episode of Behind the Music: There were no drug addictions, no affairs with each other’s spouses, no Eat, Pray, Love sojourns around the globe. To Republic, it was simply a matter of firing up a dormant machine. “As a record executive, this is the thing you dream for: a fully functional, hitting-on-all-cylinders recording artist that has a history, has a catalog, has contemporary current hits, is in the mix,” says Republic executive vp A&R Wendy Goldstein. “I knew if we did this right, this is the gift that keeps on giving: a world tour, many more albums, solo records again at some point.”

The guys are well aware of their potential. “It feels like the second bite of the apple is potentially going to be even bigger,” says Nick, “because we’re in a healthy place, we’re enjoying the ride. And I think the music is a reflection of that.”

As a grinning Kevin puts it: “Can you be nominated for best new artist twice?”

Last June, Joe, Nick and Kevin sat down in Australia -- where Joe was judging its version of The Voice -- for a combination therapy session and drinking game. They each wrote down five burning questions they’d had about each other since before their split, then dropped them into a bowl. One by one, the brothers pulled out a piece of paper and started talking -- about the pressure they put on themselves, their changing priorities, how they dealt with conflict. With each turn, the other siblings rated the honesty of the response from one to 10, with 10 being the worst, and that score was the number of seconds the answering brother had to drink.

Needless to say, within an hour, they were all feeling pretty honest. “Kevin had a few skirt-arounds” -- not shocking, given that he, like his siblings, is an alumnus of the Disney publicity school -- “so he had a few longer sips than Joe and I,” recalls Nick the morning after the March Madness show, over breakfast with his brothers.

By the time of their Australia summit, their relationship had mostly recovered. Post-breakup, Joe and Nick bought a house together in Mammoth Lakes, Calif., which resulted in plenty of quality time. Kevin’s kids also brought the siblings closer. But they knew that if they were ever going to fully heal the issues that had led to their split, they needed to dig deeper.

Nick was the one who had pushed for a hiatus -- and he was the first, during their family Christmas in 2017, to bring up the possibility of a reunion. “There’s a different magic when we’re together that I wasn’t experiencing,” he says. “So I started sprinkling some Jonas Brothers songs into my set, but always thought, ‘This would be a lot better with the other Jonas Brothers.’ ”

A month later, they reconvened at Nick and Joe’s house with members of their PhilyMack management team -- including Phil McIntyre, who had managed them in their Disney days -- to discuss the possibilities. Kevin was immediately game to return. “The idea of having my girls see me onstage with my brothers and experience that side of my life,” he says, was irresistible. Joe, who was still focused on DNCE at the time, wasn’t so sure. (He says the group is not disbanding.) But as they all reminisced about the highs and lows of their careers, they realized their story at least had the makings of a juicy documentary, and soon they started filming. “The documentary was a way for us to figure out what we wanted to say and who we wanted to be in this new chapter,” says Nick, adding that their reunion “would’ve imploded” if the documentary sessions hadn’t forced them to get all their feelings out in the open.

Everything clicked during a trip to Cuba for the doc in July 2018, when they broke out their guitars for a jam session. “We were playing ‘Lovebug’ [from 2008] in this beautiful apartment complex,” says Joe. “I was so happy. I looked at the guys and was like, ‘I’m ready. Let’s do this, for real.’ ” The documentary -- which will premiere on Amazon later this year -- will cover their reunion, as well. After our interview in Minneapolis, the brothers are due back in Los Angeles to watch the first cut. Joe is bracing himself: “I watched the teaser trailer and was crying like a baby.”

As soon as the band decided to reunite, McIntyre called Republic’s Lipman, who had worked with both Joe on DNCE and Nick on a joint venture with Island Records. Home to Taylor Swift, Grande, Drake and Post Malone, Republic Records is where an artist wants to be if they’re looking to reach the top 40. After Republic’s acts spent a combined 34 weeks at No. 1 (the final tally was 36), Billboard named it the top label of 2018 -- a title it has held for five years running.

Lipman attributes much of the success of “Sucker” to the element of surprise: “You didn’t give anybody the opportunity to anticipate or draw any conclusions about the comeback.” Goldstein compares the group’s new phase to Grande’s Sweetener and Thank U, Next hot streak, on which the singer’s impressive artistic strides coincided with heightened tabloid interest in her personal life.

The Jonas Brothers aren’t name-checking Pete Davidson (or anyone else) in their songs, but they are well aware of the public’s fascination with their romantic relationships: The “Sucker” music video shows them hanging in a lavish Victorian mansion with their real-life leading ladies, which undoubtedly helped the song along to No. 1. (The video now has more than 111 million YouTube views.) The women have also served as informal consultants on the new music. “Priyanka and Sophie love pop music and listen to Spotify’s Today’s Top Hits or Apple Music all the time,” says Nick. “So they were a really good gauge, like, ‘Does this sound good?’ ”

To figure out what the Jonas Brothers might sound like in 2019, Goldstein reached out to pop’s biggest songwriters and producers: Ryan Tedder, Greg Kurstin, Max Martin, Justin Tranter. “I remember calling Phil McIntyre back, going, ‘I haven’t had a response like this in a very long time, where everyone was just in,’ ” she says. Joe suggests that Kurstin and Tedder in particular “cracked the code” of what the new and improved Jonas Brothers were looking for: feel-good tracks (with hints of everything from ’80s new wave to reggae to country) paired with candid snapshots of their personal lives (that are also vague enough to be universal). Nick describes “Hesitate” as Joe’s love letter to Turner, while “I Believe” is a synth-heavy slow jam that alludes to his own whirlwind romance with Chopra: “People saying that we move too fast/But I been waiting for a reason, ain’t no turning back.”

“We would write a song in about 90 minutes. We would cut it in the second hour. It would be demo’d by dinner,” says Tedder, who executive-produced the project and was dubbed “the fifth Jonas Brother” by the band. (The trio has a fourth actual brother, 18-year-old Frankie, who just completed an audio engineering program.) Adds Tedder: “Sam Smith and Adele are maybe the only other acts I’ve ever worked with where they’re like, ‘Oh, my gosh. It’s 6 p.m. Let’s call it a day.’ ”

During the hunt for a first single, Tedder remembered a song called “Sucker” that he had written with Post Malone producers Louis Bell and Frank Dukes. “Louis was like, ‘Wouldn’t it be amazing if the Jonas Brothers got back together? This would be a smash,’ ” recalls Tedder. Goldstein describes playing the song for Max Martin: “Twenty seconds into it he goes, ‘You’re fucking kidding me. Holy shit!’ ”

While they were huge among teenagers and in the touring sphere, the Jonas Brothers struggled for consistent top 40 airplay during their initial six-year run. “I describe it as an allergy to the Jonas Brothers,” says Nick. Now they have the No. 1 song on the Mainstream Top 40 chart. “They’ve had celebrity,” says Lipman, “but what’s happening in this chapter of their career is the credibility in the music space.”

In their first iteration, the Jonas Brothers’ shows were heavy on spectacle, with mesmerizing visuals and intricately moving stage parts. But while their Minneapolis performance of “Cool” included confetti cannons and a marching band for a TV segment airing that night, there were no other stunts. Instead of hitting their marks and descending through the stage floor at the show’s end, the brothers spent a full minute waving to and high-fiving fans before uniting on the runway for one final bow together, celebrating what they had in that moment: the fans, the music and each other -- all, in other words, that they ever needed.

This article originally appeared in the April 27 issue of Billboard.