The Truth Behind Justin Bieber and Selena Gomez's Leaked Duet, 'Strong'

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Justin Bieber and Selena Gomez are pulling back the curtain a little bit more on their intense, on-again/off-again relationship.

A surprise duet from the superstar exes called "Strong" leaked on Drake's OVO Sound Radio this past Saturday -- which has since been taken down -- but not before creating considerable fan frenzy. The lyrics of the song seem to pointedly address the problems in their four-year romance, which both Justin, 21, and Selena, 23, have had no problem opening up about as of late.

But a source tells ET that the duet is actually not new, and was recorded three years ago for fun. And despite Justin's highly anticipated new album, Purpose, dropping on Nov. 13, the source says the tune was "never meant to be released," and "it's not appearing on anyone's album."

WATCH: Justin Bieber -- Selena Gomez Inspired a Lot of Music on My New Album

Still, the lyrics do seem to zero in on a few of the issues in their complicated relationship.

Most obviously, Justin sings about his frustrations at his partner's inability to communicate, which his current single, "What Do You Mean?" addresses in more detail.

"There's no sophistication in my lack of patience/I'm just wishing you were better at communication/As I sit here steady waiting/Wishing that you would call my name in," Justin sings in the first verse. "... What should I do? Should I go?/Who do I talk to? Nobody knows."

For her part, Selena acknowledges some fault, and the toll their busy schedules undoubtedly took on the romance.

"Wishing I was better with the distance/Wishing I was better at this damn thing/'Cause it's just been too long and I can’t change," she sings.

Justin also apparently acknowledges how deeply he felt for Selena, whom he dated on and off since 2011. "It's 'cause you're the only one I'm really missing/Nobody else would be forgiving/'Cause of all that love that you give me," he sings.

The "Where Are U Now" singer recently opened up about Selena for Complex magazine's October issue, and admitted the two were too intense, too fast.

"We were so in love. Nothing else mattered. We were all about each other," he recalled. "But when it's like that and you get your value from that, people will always disappoint you. Your girl or your dude, they’re always going to disappoint you. Your full identity can’t be in that person."

"I moved in with my girlfriend when I was 18," he continued. "Started my own life with her. It was a marriage kind of thing. Living with a girl, it was just too much at that age. When stuff would happen, I would lose my freakin’ mind, and she would lose her mind, and we would fight so hard because we were so invested in each other."

When Selena covered the October issue of Elle, she didn't rule out someday getting back together with Justin, whom she's referred to as her "first love."

"I'll forever support him and love him in a way that ... We grew up together," the former Disney star told the magazine. "I think people want it to be different. We're too young for that."

"Nobody was married," she pointed out. "There was no ... I respect him. And I think he respects me, in a healthy manner."

WATCH: Selena Gomez Is Loving Justin Bieber's Comeback: 'This Is What I Always Saw in Him'

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