Harry Styles, Zayn Malik, Louis Tomlinson, Liam Payne and Niall Horan were five complete strangers when they auditioned as solo acts on The X Factor and ended up being thrown together to create one of the world's biggest bands.
The brain child of Simon Cowell, One Direction was the juggernaut that nobody saw coming. But with their chemistry and laddish banter, it was hard not to get drawn into the 1D mania.
But just as they were at the top of their game, tragedy struck when Zayn famously quit in 2015 after five gruelling years on the road.
He explained that he wanted to be a "normal 22-year-old who is able to relax and have some private time out of the spotlight".
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His departure is said to have come as a huge shock to the group, with Liam - who turns 29 today - branding it the 'worst time' but vowing: "Us and Zayn will always remain the closest friends."
Sadly, it wasn't to be. Later that year Zayn slammed the the music of One Direction, telling Fader magazine their pop records were "generic as f***."
And in an interview with British Vogue in 2018, Zayn hinted he had fallen out with his former bandmates after they made “snide” comments about him.
He said: "I ain't spoke to any of them for a long time, to be honest with you.
"That's just the way it is. There's things that happen and things that were said after I left. Snide things. Small things that I would never have expected."
In 2016 he insisted he'd never wanted to be in the band to begin with, telling radio station Beats1: "I think I always wanted to go, from like the first year, really. I never really wanted to be there, like in the band."
He also said he "never really spoke to Harry" while they were in the group and told Billboard that he no longer talked "to any of them".
Harry spoke out about Zayn's comments in 2017, telling Rolling Stone: "I think it's a shame he felt that way... but I never wish anything but luck to anyone doing what they love.
"If you're not enjoying something and need to do something else, you absolutely should do that. I'm glad he's doing what he likes, and good luck to him."
Louis has also addressed Zayn's departure and the negative things he said about their music.
He told Metro: "I just don't think I am mature enough, even in my own head, to give that a real answer. At the moment, I am still pretty mad about the whole thing.
"I don't think [Zayn] handled it very well. But never say never. Who knows? He chatted a lot of s**t in the early days. I thought One Direction were pretty good."
Louis was devastated when Zayn didn't join the rest of their bandmates to support him when he performed on The X Factor after his mum's death in 2016.
And in an interview with The Sun in 2020, he admitted he still doesn't feel ready to reach out to his former friend.
"I've not actively tried. We've all got a lot on our plates and there might be a day where I wake up and think: 'OK, I want to right that wrong', but not yet," he said.
For Liam's part, he told GQ magazine that he'd had a hard time wrapping his head around the way Zayn left.
He explained: Liam: "I think with Zayn's particular exit and the way he chose to go, we haven't really heard from him since he left. He didn't even say goodbye, if I am being honest. It was a really sordid scenario, from our side certainly. A bit strange. It's difficult."
And Niall hinted that while he'd tried to keep in touch with Zayn, it hadn't quite worked out as he'd hoped.
"As long as I've known him, Zayn's been the hardest man to stay in touch with," Niall told GQ.
"Then we had a falling out a few years ago and, to be honest, that's just the dynamic: You have people you are friends with and people you are not."
So where do they all sit now?
One Direction fans were heartbroken when Zayn failed to join the group to celebrate their 10th anniversary in July 2020, with Liam telling the Jonathan Ross Show: "When he left, it wasn’t on great terms so I don’t feel like it’s a thing. If he didn’t want to be here, he shouldn’t be here, which is fine."
However, there appeared to have been a thawing as when Zayn and girlfriend Gigi Hadid welcomed their baby daughter in September 2021, the lads reached out with Liam - who is a father to son Bear, three, with ex Cheryl Tweedy - giving the couple a shout out on Instagram Live.
"Oh yeah congratulations Zayn and Gigi as well actually yes, very lovely news this morning. Bless them, starting a family," Liam gushed, showing no trace of hard feelings.
Niall also confirmed he'd sent a message, hailing the little one's arrival an 'amazing thing' while Louis 'liked' their baby announcement on social media.
And Zayn actually threw some love Niall's way, revealing he's the only former bandmate whose music he listens to.
He told SiriusXM: "Ill tell you what, Niall is my favourite. How about that? There you go. Niall makes the best music, there you go.
"Yeah, I will say that he makes better music than me. Yeah, I'm a Niall fan."
Then in May this year, Harry appeared to throw out an olive branch, insisting there is a 'respect' and 'deep love' between all five, despite the mud that has been thrown.
Making a peace offering in an interview for Apple, he told Zayn Lowe: "You know I look at people who kind of went through some version of what we went through but on their own. And I'm like, I can't imaging having done that.
"I feel like there's very much a respect between all of us. We did something together and that is something that you can't really undo. It's a very deep love for each other, I think."
Do you think all five members of One Direction will ever reunite? Have your say in the comments section below...
