It wasn't to be a global pop star and heartthrob.

Or date models and celebrities, perform on Broadway and act on television.

All that has happened to the Gold Coast-born Simpson.

But his dream was to swim for Australia - just like his parents.

Simpson's mother, Angie, raced for Australia at the 1987 Pan Pacific Games.

His father, Brad, swam for Australia at the 1994 Commonwealth Games.

Simpson himself won two gold medals at the 2009 Queensland swimming championships.

But that same year, Simpson - who as a seven-year-old asked for guitar lessons after watching his dad strum and sing at backyard barbecues - uploaded some songs to YouTube.

They came to the attention of a Grammy-nominated record producer in the United States, Shawn Campbell.

Simpson was signed by Campbell's Atlantic Records and the-then 13-year-old and his family relocated to Los Angeles in 2010.

As he now puts it, his swimming dream was "sidetracked".

In 2011, Justin Bieber's manager lured Simpson as a client: the Australian teen toured around the US with pop icon Bieber, made it onto the Billboard charts, released EPs to acclaim.

He was a shooting star in the pop world.

Worldwide tours to swooning audiences of predominantly teenaged girls followed, as did merchandise ranges including Cody dolls.

His fame parlayed into cameos on American television sit-coms, appearances on US television staples such as Good Morning America and Dancing With The Stars, and a lead role in a Broadway musical.

Romantic relationships accompanied his celebrity status, dating model Gigi Hadid and fellow pop star Miley Cyrus.

Yet Simpson was unfulfilled. He wanted to swim for Australia.

So in 2019, he returned to the pool in chase of his dream.

"My mum swam for Australia and I told her as a little boy that I wanted to swim for Australia as well," Simpson said.

"And then obviously I was sidetracked for the better part of 10 years.

"When I decided to come back (to the pool), she was one of the only people to say 'are you sure you want to do that, do you understand the work it entails?'."

Simpson returned to his pet stroke, butterfly, thinking by 2024 he may have a chance of earning a berth on an Australian team.

Such has been his astonishing progress, that selection came on Wednesday night at the Australia championships when he qualified for the 100-metre 'fly for the Commonwealth Games in July-August.

The honour stunned Simpson, who is also a likely discretionary pick for the world titles in June.

"It means everything to me," he said.

"I certainly didn't even expect it to even be a possibility until 2024.

"So the fact that stuff has started to happen so quickly, so early, is just unreal.

"I have come so much further than I expected so quickly.

"But I think about it every morning, every night, and I work towards it every day so I was bound to hopefully reap some rewards at some point."

Music remains a passion Simpson, who now dates Australian swim star Emma McKeon.

Last month he released another album, self-titled.

On streaming service Spotify alone, he has 2.8 million monthly listeners - many, no doubt, are among his 4.4 million followers on Instagram.

But now aged 25, music is secondary to his now-realised swimming dream.

"It (music) is just on the backburner for now," he said.

"I released an album a month ago so it's still something I like to do.

"I think every swimmer, it's important for them to have something outside of the pool to balance your life out."

That statement echoes the sentiments of his swim mentor, Australian legend Ian Thorpe.

"Ian Thorpe is always telling me if you stop playing music, I will stop mentoring you in the sport, you need to have something to go to in life," he said.

Australian Associated Press