When Justin Bieber performed at St. Paul’s Jingle Ball concert in 2009, a preteen boy in the crowd from Stillwater named Jonah Frantzich decided right then and there that he wanted to become a pop singer. He has returned to KDWB’s holiday party nearly every year since then, too, always with his kid sister Esther in tow.

“So this year is really going to be special for the two of them,” said Carrie Frantzich, Jonah’s and Esther’s mom.

That’s because this year Jonah will be on stage at Jingle Ball, and not just in the crowd.

At 19, the singer — who got his start performing live over the internet from his bedroom — is one of five young men in the fast-rising new boy band Why Don’t We, part of Monday’s Xcel Center lineup.

Scheduled at the ball alongside Kesha, Charlie Puth, Halsey and not one but two One Direction castaways, Why Don’t We is aiming hard for the gaping hormonal and commercial hole left by the hiatus of One Direction. The quintet formed last year in Los Angeles, when its high-school-age members were mostly all strangers brought together via the same management team.

In just over one year, WDW has put out five digital EPs, including a new holiday collection and an eponymous mini-album that took over the No. 1 spot on the iTunes pop chart from none other than Harry Styles in June.

They also landed a deal at Atlantic Records and now count former AEG Live CEO and Michael Jackson confidant Randy Phillips as a co-manager.

Amid all the hubbub, that Stillwater youth who wanted to be Bieber seems to have kept an un-Bieber-like level-headness.

“We’ve really been working together and working hard, just making sure we’re ready for what’s to come,” said Jonah, who goes by the stage name Jonah Marais in the group using his middle name (a nod to the North Shore hamlet of Grand Marais by his parents).

Jonah cut out for Los Angeles a year ago September, when he moved into a house with each of his new bandmates. They developed a camaraderie right away, he said, since they each “shared very similar tastes in music and ideas about what we want to accomplish.”

“Since then we’ve pretty much hung out together nonstop, writing songs together, singing together, jamming together,” he said.

Calling from Dallas on Monday a night before the first Jingle Ball date — St. Paul is one of a dozen cities on the iHeartRadio ball tour circuit — Jonah used that night’s accommodations to exemplify the band’s “togetherness” over the past year.

“Zach’s from here, so we’re all staying at his [parents’] house tonight,” he said, referring to his Texan bandmate Zach Herron. They’ll do the same in Minnesota, where Jonah just spent a week around Thanksgiving.

“It was great to be home, but it felt like a whole other world at first being out of the fast lane. For like the first two or three days, I was stressing, thinking I needed to be doing something. But by the end of the week, I was falling asleep on the couch anytime I wanted.”

Family ties

Jonah isn’t the only one in his family to break into the music business. His dad, Timothy Frantzich, is part of the regionally known sibling folk duo the Brothers Frantzich. And his cousin, Whistler Allen, is the drummer in the nationally buzzing indie-rock quartet Hippo Campus.

The elder Frantzich recounted how the family — with one brother older than Jonah and two younger sisters — would sometimes sing together at concerts or as street buskers, which he figures gave his son the performance bug.

“He was always very comfortable with singing in front of people and never got flustered by it,” Tim Frantzich said.

Ironically, the children in the family had very limited access to TV and the internet growing up until it became necessary for school. And that’s when Jonah got a whole other kind of education that would come in handy for his chosen profession: He started using the livestreaming app YouNow to sing and play piano for viewers across the internet.

“He came down one day and said, ‘I just had 56,000 people watching me sing online,’ ” Carrie recalled, still sounding surprised by the moment. “He was as good at networking as he was at the music, which also came in handy.”

Most of Jonah’s bandmates in Why Don’t We earned industry attention through similar viral methods, also including YouTube. One of them, Daniel Seavey, made it into the top 10 on “American Idol” when he was only 15 during the Fox TV show’s 2015 season.

Jonah earned enough of an online following to pack the Amsterdam Bar & Hall in St. Paul for his first real solo concert in 2014. He also sang to about 5,000 fans (mostly girls around his age) at the DigiFest concert at the Minnesota State Fair grandstand in 2015. Along the way, he quit school at Minnehaha Academy during his sophomore year to earn his diploma online and openly pursue music offers around the country.

While his outlook as a solo act looked promising, Jonah said he reacted to the idea of starting the group just as their band name suggests: “Why don’t we?”

“It seemed worth a shot to at least try it at first,” he said. “And then we knew pretty quickly we were all a good fit together. It worked out well almost from the start.”

Taking a cue from the new generation of hip-hop acts that the members all count as inspiration, WDW started issuing songs online almost immediately. They landed huge viral numbers with “Something Different” and then Top 40 radio play with “These Girls,” each featuring members alternating on vocals in classic boy band fashion. They started popping up on TV, too, including NBC’s “Today Show,” MTV’s “TRL” and Nickelodeon’s Halo Awards.

Also almost from the get-go, the group earned blessing-or-curse attention as possible heirs to the One Direction throne. Jonah said they’re cool with the comparisons.

“We all have huge respect for their music and everything they accomplished,” he said, “but at the same time we take a lot of pride in doing things our own way. We’re going to be doing things that a lot of people don’t expect from a quote/unquote boy band.”

Case in point: WDW will follow up its Jingle Ball appearance with a full-length concert March 6 at First Avenue nightclub, not usually a stop on the teen-pop circuit. The show sold out right away.

“[Management] asked me where I thought we should play, and I said, ‘It definitely has to be First Ave!’ ” Jonah said.

Clearly, this kid was brought up right.