Little Mix star Jade Thirlwall says the band would fall apart if one of the members quit.
The chart-topping girl group formed on The X Factor in 2011 and have since sold millions of records around the world.
While another famous girl band, the Spice Girls, carried on following the departure of Geri Horner, Thirlwall ruled out the same happening with Little Mix.
The group feature on the cover of May’s Cosmopolitan and Thirlwall told the magazine: “It’s all or nothing with us. We are sisters so if one of us left, that would be it.”
In a wide-ranging interview, the band – made up of Thirlwall, Jesy Nelson, Leigh-Anne Pinnock and Perrie Edwards – discussed their famous boyfriends, body image and living in the public eye.
Thirlwall, from South Shields, said she felt “like a boy” next to the other members.
“I didn’t have a very womanly shape and I’ve got no tits,” she said. “I’ve kind of grown into myself a little bit now but I used to want a boob job. I (felt) that I wasn’t sexy enough in the band.
“I still have that complex now when I go on dates. I think, ‘Am I woman enough for someone?’ which is silly.”
Last year, Nelson was widely praised for appearing in a BBC documentary revealing the devastating impact online trolls had on her.
She told Cosmopolitan one of the downsides of fame is having “so much to think about 24/7”.
“You can never let yourself go,” Nelson said. “I want to go on holiday, eat shit and let my belly rolls out without worrying that someone’s taken a sneaky photo. You’re always being judged.”
Pinnock and Edwards are both in relationships with Premier League footballers and told how their busy schedules make it difficult to see loved ones.
Edwards, whose partner is Liverpool midfielder Alex Oxlade-Chamberlain, said: “As soon as we get a day off, the thought of having to drive to Manchester is an effort. But because I want to make it work and I absolutely adore him, I just grin and bear it.
“It’s hard. I always say to management if we haven’t got two days off back to back, I won’t see my boyfriend.”
Pinnock is with Watford striker Andre Gray and said: “I feel like I don’t have a normal relationship. I live with my boyfriend and still don’t see him.”
The May issue of Cosmopolitan is on sale from March 26.