What started with the most innocuous of beginnings—George Sheppard helping his sister Amy with a college assignment to write and record a song—reached a tipping point several years later with the reception of “Geronimo.”

Their band, Sheppard, had a song on its hands that debuted at No. 31 on the Billboard 200, on its way to numerous gold and platinum certifications worldwide. It would be correct to assume the two South Pacific siblings never envisioned this while working on that original assignment. It was never even his goal to start a band, George Sheppard said by email from his native Australia.

“I came home [in 2009] to Brisbane one time from living in Sydney and Amy had this uni assignment,” he said. “It quickly became apparent that our voices blended really well together. I think being siblings, our vocal chords are similarly built, so the harmonies sounded particularly nice. Dad could hear us singing from the lounge room. … [He] was so impressed that he offered to pay for some recording studio time. The very beginning moment of Sheppard as a musical act.”

The siblings, including younger sister Emma, grew up in Papua New Guinea, where their father is an attorney. He had an ear for music, however, and played piano in his younger days. “He’s super happy that we formed the band,” Sheppard said. “It means he gets to live a musical life vicariously through us.” It was a beautiful life sometimes marked with dangers, he said, so the family eventually moved south to Brisbane, Australia.

The World War II history of the South Pacific must have intrigued the siblings, because somewhere along the line they learned the yell of American paratroopers jumping from airplanes: “Geronimo!”

The irresistibly catchy up-beat track of the same name, which was included as the opener on the band’s 2015 debut album, Bombs Away,” propelled the band to heights the members—which include Emma Sheppard (bass), friends Michael Butler, Jason Bovino (guitars) and Dean Gordon (drums)—much higher than they had anticipated.

When the time came to write a follow-up, they couldn’t come up with anything like “Geronimo,” George Sheppard said. Eventually, the band had to approach the music from a different perspective. Fans will get their first taste of the songs from the new album, due in early 2018, when the band begins a two-week U.S. tour at Rickshaw Stop in San Francisco.

RIFF: When you have a song do as well as “Geronimo,” do you have any fear of matching a prior success? How do you overcome that?

George Sheppard: Honestly, yes. It’s hard not to feel some kind of follow-up pressure when you’ve written a song that went gold [or] platinum in over 30 countries. We went through a period where we couldn’t write anything after the release of “Geronimo.” The song was so successful that we were scared whatever we’d write next just wouldn’t be as good. It made us super-picky with what songs we did spend our time on; if it wasn’t clearly another “Geronimo,” we simply didn’t bother with it. Obviously, this is a bad way to think about writing music because every song takes on its own different personality and life form. We realized at the beginning of last year that trying to replicate the success of “Geronimo” was a bad way of approaching this next album, and that we needed to get back to writing music for ourselves again. We had to shake off that idea of needing to follow up a massive international hit and just get back to the mental space we were in before we’d had any success. After we shifted our mentality and expectations, the songs started flowing again, and we wrote an album, which, in my humble opinion, is an evolution of “Bombs Away.”

I don’t think I know anyone from Papua New Guinea. What was your first home like?

Papua New Guinea was a pretty unique place to grow up. I left for boarding school when I was 12, so I have plenty of memories of PNG. It’s a beautiful country, and the people are lovely, but it’s not the safest place in the world. We always lived in large compounds complete with guard dogs and barbed wire [or] electric fences. We went through some pretty scary moments growing up, but for the most part it was an awesome childhood. It’s the kind of place where everyone knows each other; there was a real sense of community. And the boating was incredible. Every Sunday, everybody would take their boats out to the gorgeous islands surrounding Port Moresby and go jet-skiing and snorkeling. Our father still works up in PNG, so we try to go back every so often and do shows there. It’s always very surreal to be back!

What song do you have yet to release should your fans be excited to hear right now, and why? What does it sound like?

The album opener, “Coming Home,” is my favourite song we’ve ever done and I honestly can’t wait for people to hear it. It’s about that exciting moment you touch down at home after a long tour. It’s incredibly anthemic, explosive and euphoric. [It] feels so good to open the show with it.

What else are you into besides music?

Outside of the band, I’m a pretty regular 29-year-old guy. I’m a huge movie buff. The cinema is one of my favourite places to be. I love tennis, and I play a lot of squash. I’m also into indoor rock-climbing. I’m a pretty big technology enthusiast as well. I’ve got all the gadgets: a hoverboard, a virtual reality system, smart watch—you name it, I’ve got it. Oh, and I think Rick and Morty is the greatest TV show of all time.

What’s it like being on the road together; what are the benefits of touring with family?

Being on the road together is usually a lot of fun. We’ve made some really special memories over the years that will last a lifetime. That being said, there are tough days when all you want to do is be alone, but it’s almost impossible to get that space. As long as you’re considerate towards the other people in the touring party, everyone gets along. Touring with family is great, because it helps a lot with the homesickness, not to mention it’s great to be on the road with people that you can 100-percent trust; people you know will have your back if shit hits the fan.

Do you have any favorite experiences in the San Francisco Bay Area? Have you spent much time here before?

I know it’s probably a bit cliché, but seeing the Golden Gate for the first time was a mind-blowing experience. Photos do not do that thing justice. It’s SOOOO big, it just didn’t feel real. We also got to visit the Google campus and play them a show, which was amazing. That company definitely knows how to take care of its employees! I really want to do Alcatraz this time around… hopefully we get a chance to go exploring!

Follow Roman Gokhman at Twitter.com/RomiTheWriter and RomiTheWriter.Tumblr.com.