Hear 'Bachelor' Colton Underwood's Catchy New Song With O-Town! (Exclusive)

O-Town with Jacob Underwood

'The Bachelor' hunk talked to ET about battling nerves to make his singing debut on the band’s long-awaited new single, ‘Hello World.'

And, then there were five!

O-Town has briefly become a quintet again. However, the fifth member isn’t former member Ashley Parker Angel, but none other than The Bachelor star and former NFL player Colton Underwood, who features on the group’s new single, “Hello World,” premiering exclusively on ET.

“We’ve been five members before, so I think it was natural for us to have a pretty blonde guy in the band!” Jacob Underwood, 38, tells ET. “I was kind of jealous because I think his eyes are bluer than mine, so I’m going to have to do something about that.”

The surprise collaboration came about after Colton asked Jacob -- whom he met at a charity dodgeball event back when he played football for the San Diego Chargers -- to write him a fundraising song for the Colton Underwood Legacy Foundation, which assists cystic fibrosis patients.

Colton and his family are intimately familiar with the debilitating condition, which primarily affects the lungs, due to his 7-year-old cousin, Harper, suffering from the illness. Colton, 27, started the foundation in Harper’s honor.

Meanwhile, Jacob and his bandmates (Dan Miller, Erik-Michael Estrada and Trevor Penick) had been busy working on their forthcoming album, OTWN, expected to drop this summer. "Hello World" is the first of seven new tracks which will combine with the group's 2017 Part 1 EP to complete the OTWN record, named after the title track which stands for On The Way Now.

Having toyed with a song concept around “Hello World” for a year, Jacob hit a wall with the track until he sat with Colton and learned about how his foundation has helped provide funds and equipment to cystic fibrosis patients and also launched the Legacy Project, which provides AffloVests to those in need. The portable, battery-operated vests help loosen and clear the buildup of mucus in the lungs of cystic fibrosis patients, known as “CF warriors,” and the project inspired the song’s opening line, “I am a warrior.”

“I kept having problems with the verses because I’m not sure where the line, ‘Hello world,’ came from. To me, it was coming of age, realizing my priorities weren’t straight and needing to focus, meaning I had a better view of the world and who I am in it,” says Jacob, who welcomed his first child, adorable daughter Everest, with fiancée, Chandler Bay, in October. “But I couldn’t put that down in a verse. Then as Colton and I were talking about these kids, it became about not sitting around, but taking the time you have and making the most of it. And, how the more we learn about the suffering and the things that people have to deal with -- it gives you a new perspective, gratitude and makes you want to help people.”

Colton helped Jacob write the track, which they hope will serve as an anthem for cystic fibrosis patients and others battling physical and mental illnesses. While Colton wasn’t planning to sing on the song, Jacob had other plans.

“He said, ‘I can’t sing for sh**! But I want to be in the studio,’” Jacob recalls. “I was like, ‘Sure, come on down,’ so of course we had to throw him behind the mic. I had to see for myself whether he can sing or not. I was like, ‘Don’t worry, man, we all use auto-tune nowadays!’ -- joking with him to make him feel comfortable because it’s daunting getting behind a mic with 15 people staring at you. He’s a ham and played up to it, though. His energy in the studio was just fun. You could tell he hadn’t been in there before, so was asking all these questions.”

“They’re such great people, so I hopped behind the microphone and that’s a credit to them for encouraging me and making me feel comfortable enough to do that,” Colton tells ET. “It was such a fun, cool environment and for a great cause, so it was just a time to let loose and have fun.”

“Of course I was [nervous,]” Colton adds. “It took me two or three runs through the song to even get a little bit comfortable and even now, I’m nervous just thinking about it!”

Colton sang the line, “I want to see you learn," which Jacob and his co-producer cut and sampled to create a synth break that plays two minutes and eight seconds into the song, after the second chorus.

“I had goosebumps when Jacob and I were going back and forth writing lyrics because I knew how powerful it could be, then hearing the final cut was amazing,” Colton says. “I still get goosebumps every time I listen to it.”

'Bachelor' star Colton Underwood in the studio with O-Town. - O-Town

With O-Town now touring the U.S. with shows through till July, the big question is whether Colton might make an appearance on stage with the band, who performed the track for the first time at a recent Kentucky show. “Anytime he’s in the neighborhood for an O-Town show, I can guarantee we’re going to drag him up there,” Jacob teases.

“For sure!” adds Colton about whether he’d jump on stage with the guys.

The former athlete and reality star is well-equipped for boy band life given he grew up listening to groups like the Backstreet Boys, who have previously appeared on The Bachelor. “Growing up, I was a big *NSYNC and Backstreet Boys fan, but I did pay attention and listen to O-Town, too,” he says. “Since then, I’ve been big into pop. I’m big into music in general, but I love pop, I love country and I like some hip-hop too.”

“It’s oddly similar to my athletic background,” Colton adds, about what he has learned from O-Town about being in a boy band. “Just knowing that you have that camaraderie and that safe place to express your feelings and that you’re going through it with other people and help pick each other up. I think a boy band embodies everything we want this song to stand for -- you’re in this together, stand up for who you are, express yourself and don’t wait on opportunities; go get them and chase life.”

As for welcoming another blonde, blue-eyed hunk into the group, it’s only natural that Jacob and Colton share some physical similarities given that they recently discovered they may be long-lost cousins!

Having joked about their shared surnames since they met, Jacob thought the odds of actually being related were slim given that his family is from the tiny Illinois towns of Carbondale and Murphysboro, where chances are they would know other Underwoods. But while hanging with Colton and his clan in San Diego eight months ago, it turned out they may be closer than they think.

“I was talking to his dad and was like, ‘Let’s get to the bottom of this -- are you guys from Colorado or did you move there?’” Jacob says. “He goes, ‘Well, we all moved to Colorado from this little town in Illinois -- Murphysboro and Carbondale.’ I looked around and said, ‘Did one of you say something to him? Are you all messing with me?’ So now Colton and I are like, ‘23andMe -- we gotta do it!’”

“We’re both curious as to what distant cousins we are,” Jacob continues. “We have a lot in common personality-wise … and we got those blue eyes!”

Now that they’re potentially family, it’s only natural that Jacob and his musician fiancée, Chandler, have a vested interest in The Bachelor. In fact, all of O-Town is hooked on the current season of the ABC series.

“Last week we were at rehearsal at Dan’s house in Phoenix and Dan and his wife always tell us how dramatic the seasons are,” Jacob says. “We live-streamed us watching and it was hilarious because it was Trevor’s first episode and now he’s hooked. About 15 minutes before the redhead girl [Elyse] quit, Erik was like, ‘She’s my favorite. She’s going to win.’ My pick was Hannah G, then Cassie. Both seemed like a good fit -- normal, easy to talk to and fun.”

“I think it was a no-brainer to pick him,” adds the Dead 7 star, about what makes Colton the perfect bachelor. “Knowing his family, where he comes from, where his heart is and how hard he works -- those are all great traits for a husband. He’s ready to settle down and any girl he picked would be lucky because it’s hard to find a good guy in this line of work who is actually sincere about the passion of it, not just the fame and what it can bring monetarily. The Bachelor has allowed him to show who he really is and how deep that goes. People say he’s playing to the camera, but he’s not -- he really is that sweet and sincere.”

And, if things don’t work out for Colton on The Bachelor, he can always try and find love on tour with O-Town.

“Yeah, I might get him out on the road and see if he can dance now!” Jacob says with a laugh.

“Hello World” is out on iTunes and Spotify on Feb. 22, with all proceeds from the track going to the Colton Underwood Legacy Foundation.

Colton hit the studio with O-Town members, Trevor Penick, Dan Miller and Jacob Underwood, in January to record "Hello World." - O-Town