Gwyneth Paltrow and Chris Martin were "off and on for many years" before separating.
The former couple - who have children Apple, nine, and Moses, seven, together - announced last week they were splitting after 10 years of marriage, and insiders admit they weren't surprised by the announcement.
One source said: "They were physically separated and emotionally."
Another source added to People magazine: "They have been on and off for many years. The marriage was falling apart."
The 'Iron Man 3' star and her Coldplay rocker spouse had successfully managed to juggle their busy careers and family life but friends say it was impossible for them to keep maintaining a balance.
A source said: "They seemed to have a pretty mature handle on that crazy rotation of being superstars and parents. But that balance, given the time they had to spend apart, clearly couldn't sustain itself."
And another friend thinks Gwyneth and Chris' different personalities also played a part in the problems with their marriage.
The insider explained: "[Chris] is the kind of person who is always in a T-shirt. She's much more glam."
Despite their split, the pair have vowed to stay friends for the sake of their children and are currently enjoying a family vacation.

Britain's Prince Harry hosted a boys' night out at London's Arts Club.
The 29-year-old redhead threw a "private little get together" for his close friends at the exclusive venue on Tuesday evening (04.01.14), where guests dined on a hearty meal of chicken and chips, washed down with white wine.
A source told EntertainmentWise: "Last night was lovely, but it was just a private little get together at the Arts Club, it wasn't for charity or anything like that. Cressida [Bonas] wasn't there but a lot of his rugby friends were as well as a few others, it was just a quiet little night."
Harry was reportedly joined by his pal James Haskell, while presenter Lizzie Cundy and 'Made In Chelsea' star Mark Francis Vandelli were also hanging out at the same nightspot.
The handsome royal has been busy catching up with old friends in recent weeks since returning from his charity South Pole trek this winter.
He sent fitness enthusiasts into a frenzy last month when news emerged he had joined a London public gym called Third Space, which costs £139 a month to use.
Harry's security was forced to step in when the star was mobbed by fans trying to take pictures of him working up a sweat on the treadmill.

Radiohead are planning their ninth studio album.
The 'Karma Police' hitmakers have been focusing on solo projects but guitarist Jonny Greenwood has confirmed they are heading back into the studio to record new material.
In an interview with Nashville Cream, the 42-year-old musician said the band will "make a plan" and are getting together later this year.
He said: "Well we're meeting up at the end of the summer, and we'll make a plan. But, you know, we're a slow-moving animal, always have been. I guess we'll decide then what we do next."
Earlier this year, Jonny's brother Colin, the band's bassist, said Radiohead's plans for a new record were still "up in the air" as they were all busy working on side projects and frontman Thom Yorke had recently come back from touring with his supergroup Atoms For Peace.
The band - also formed of Ed O'Brien and Philip Selway - intend to embark on a tour as soon as their new record, the follow-up to their 2011 record 'The King Of Limbs', is released.
Meanwhile, Jonny will continue to play concerts with the London Contemporary Orchestra and admits its "a bit exclusive".
He said: "You're sort of insisting that people have to be there. There's a snobbery to that, which is a shame, but yeah, it's funny."

Red Hot Chili Peppers' bassist Flea is set to release his autobiography.
The 51-year-old musician has signed a deal with Grand Central Publishing and the book will focus on his early life, battle with drug addiction, life on the road with the band mates and his career in film.
According to Time.com, the autobiography will also see Flea "share stories from his intense and dynamic life, including: his move from a 'normal' upbringing in the suburbs of New York to Los Angeles to live a bohemian life with a jazz musician step-father," along with "his young, rebellious life on the streets of LA."
Flea will be the second member of the band to pen his own tome, following in the footsteps of frontman Anthony Kiedis, whose 2004 memoir Scar Tissue reached number one on the New York Times' Bestseller List.
The as-yet-untitled autobiography, which has not yet been given a release date, also promises to feature "details about his sometimes complex friendship and collaboration with Kiedis, his myriad experiences with hard drugs, and, of course, the tumultuous creative journey of the legendary Red Hot Chili Peppers through its various incarnations over the last 30 years."

Tom Riley will guest star in the new series of 'Doctor Who'
The 'Da Vinci's Demons' actor will star in an upcoming episode of the sci-fi series alongside Peter Capaldi - who is yet to make his debut as the Time Lord - and Jenna Coleman, in one of two episodes which have been penned by actor and screenwriter Mark Gatiss, and filming will reportedly begin soon.
Expressing his excitement over the project, Tom wrote on Twitter: "Well that's out then. I've been a massive fan since I was even smaller than Jenna. Very excited. @Markgatiss's script is awesome. #DoctorWho (sic)."
The 32-year-old star's comment came after the official 'Doctor Who' Twitter account confirmed rumours that he'd be joining the cast on a short-term basis.
The post read: "Tom Riley will appear in the new series of Doctor Who, starring in an episode written by Mark Gatiss".
Meanwhile, Gatiss - who has created six episodes of the BBC One series in the past - has confirmed that he's written the scripts for two more episodes but confessed he's unsure as to whether both will feature in the new series, which is expected to air later this year.
He wrote on Twitter: "To clarify. I've been commissioned to write two episodes of 'Doctor Who'. That doesn't mean they'll both necessarily be in this season."
'Sherlock' writers Steven Moffat and Steve Thompson are also among the list of names confirmed to be writing for the new series.

Jordan Stephens has landed a role in new E4 drama 'Glue'.
The Rizzle Kicks singer will make his acting debut later this year in the home-grown drama series set in the English countryside, created and written by Skins' Jack Thorne.
The 'Lost Generation' hitmaker is just one name among the many young talents from British film, TV, stage and music who have been picked for the murder mystery show.
Jessie Cave, best known as Lavender Brown in the 'Harry Potter' franchise, 'Submarine' star Yasmin Paige, Callum Turner from ITV drama 'Leaving', Charlotte Spencer of 'Line of Duty' fame, 'Fresh Meat' season three newcomer Faye Marsay, 'Starred Up' actor Tommy McDonnell, Bristol Old Vic graduate Billy Howle, and 'Waterloo Road' star Tommy Lawrence Knight have all been cast in the upcoming show.
They will also be joined by Kerry Fox ('Bright Star'), Jonny Owen ('Shameless'), Kierston Wareing ('Luther'), and Steve Oram ('Sightseers').
Sophie Gardiner, Channel 4 Commissioning Editor, commented: "The team at Eleven have pulled together an incredible cast for Jack's thrilling scripts - the line-up reads like a roll-call of some of the brightest up-and-coming talent around. We can't wait for them to bring our bold new series to life. Brace yourselves for a trip to the countryside... E4-style."
The show is set in small farming village Overton, where bored youngsters risk their lives by playing deadly games and when the body of a local teenage boy is found underneath a tractor, everyone is forced to confess their darkest secrets, changing the face of their small community forever.
'Glue' is scheduled for release in the autumn of 2014.

Sam Faiers will reportedly star in her final episode of 'The Only Way Is Essex' tonight (02.04.14).
The 23-year-old reality TV star is said to have decided to quit the ITV 2 show in order to focus on her relationship with ex-fiancé Joey Essex and keeping healthy since being diagnosed with Crohn's disease earlier this year, and as tonight's episode is the last of the season it could be her final appearance.
The series finale will see the stars - which include Sam's sister Billie Faiers and her pal Ferne McCann - get dolled up for the wrap party and according to the Daily Mirror newspaper Sam, dressed as a princess in a glittery gown and tiara, will make an emotional exit.
Meanwhile, James "Lockie" Lock will take inspiration from romantic film 'Pretty Woman' in an attempt to win back his ex-girlfriend Danielle Armstrong - who he split from during the current series after it was revealed he'd cheated on her during the early stages of their relationship.
Donning a smart navy suit and carrying a bunch of red roses, Lockie will recreate a scene from the movie which sees Richard Gere attempt to woo Julia Roberts' character by hanging out of the roof of a limo and declaring his love for her.
Ricky Rayment will also feature in the finale to the explosive eleventh series when he's welcomed into his girlfriend Jessica Wright's family by her cousin Elliott, who he's had a number of disagreements with throughout the series.

Amy Adams is set to star in a sci-fi thriller.
The 'American Hustle' star is in early talks with 'Prisoners' director Dennis Villeneuve to appear in 'Story Of Your Life', which is based on a short story written by Ted Chaing, Deadline reports.
The story, which has a script written by Eric Heisserer, is set at a time after alien crafts land around the world. An expert linguist - who Adams would play - is recruited by the military to figure out whether they are a threat or have come in peace.
As she slowly learns to communicate with the aliens, she is subjected to a series of vivid flashbacks that are key to understanding the mystery behind the real purpose of their visit.
FilmNation Entertainment, in partnership with Lava Bear Films, are financing, producing and handling worldwide sales for the project.
The companies will produce along with 21 Laps' Shawn Levy and Dan Levine, and the scriptwriter will serve as executive producer.
The film's director recently said he hopes the movie will tell an "inspiring" story.
He said: "It's very poetic, and a strong take on an alien landing on Earth. It's very original, very fresh and very inspiring.
"I'm very excited about that project. I'm supposed to shoot it at the beginning of 2015."

Russell Crowe has met with a U.K. Church leader to discuss 'Noah'.
The Academy-Award-winning actor reportedly held a "short private meeting" with the Archbishop of Canterbury ,Justin Welby, to discuss the religious issues raised in the Darren Aronofsky-directed epic.
The pair met at Lambeth Palace in London for talks after the film's UK premiere on Monday (31.03.14) just weeks after his visit to see Pope Francis in Rome last month.
Taking to Twitter, Archbishop Welby described the meeting as a "great visit" and praised the actor's sense of humour, as he wrote: "Great visit from @russellcrowe, talked about Noah and his films. He spoke to as many people as possible, sense of humour, impressive. (sic)"
The Archbishop didn't pass public judgment on the film but The Telegraph newspaper reports he found it "interesting and thought-provoking".
The Hollywood blockbuster - based on the bible's Genesis story of Noah's Ark - has opened at number one in the U.S box office despite backlash from some Christian and Jewish groups who have criticized its loose interpretation of the familiar biblical story.
Several countries including Pakistan, Bahrain, Qatar, UAE and the Middle East have also banned the film for conflicting with Muslim principles.

Sam Claflin wants to meet a ghost since shooting horror film 'The Quiet Ones'.
The 27-year-old actor stars in the supernatural thriller about a professor who wants to disprove the notion that paranormal activity is caused by the undead by creating his own poltergeist from negative human energy.
Rising star Sam - who has also starred in 'Snow White and the Huntsman' and 'The Hunger Games' franchise - has become fascinated by ghouls and ghosts since making the movie and is hoping a spectre will haunt him soon.
Speaking at the movie's premiere in London's Leicester Square on Tuesday night (01.04.14), Sam told BANG Showbiz: "Literally since this movie has come out I've heard a lot of spooky things but nothing never personally but it's something I'm intrigued by. I want to know more, I want to learn more. I can only hope one day some ghost out there will decide to haunt me."
Sam thoroughly enjoyed shooting John Pogue's Hammer horror film and believes the project benefited from having a small, tight-knit cast.
He said: "A smaller cast made the filming process, the chemistry was really nice, it was there and there was no hard work in that sense. It was much more fun experience; despite it being a scary movie we had a lot of laughs. Trying to keep a straight face was hard, because the cast knew each other so well."
Sam's co-star Jared Harris - who plays ghost-creating Professor Coupland - agreed with him praising all the actors who had to cope with a gruelling production schedule.
Jared said: "The company of actors we had was a really good group; we had good energy with each other and we had good camaraderie. We all really enjoyed each other's company.
"We had to shoot the movie in around four weeks in six day weeks, we were all under a lot of pressure. Luckily on this film we had two weeks of rehearsals, but it was a tough schedule to keep up with."
Other stars of 'The Quiet Ones' who walked the red carpet included Olivia Cooke and Rory Fleck-Byrne.

Miranda Kerr wants to "enjoy" her body "while it lasts."
The former Victoria's Secret model - who has three-year-old son Flynn with ex-husband Orlando Bloom - says she is comfortable stripping down to her underwear because she "loves" her figure and while she would love to have larger breasts, she is happy to flaunt her toned physique while she is still young.
Speaking in the May issue of Britain's GQ magazine, Miranda said: "I won't have a body like this forever so I may as well enjoy it while it lasts. I love my body, look after it and enjoy all the changes it goes through.
"I loved having a bigger chest while pregnant and I'm lucky to have a small frame. I'm a healthy juicy person."
However, Miranda, 30, does admit that her figure has become noticeably less toned now that she is having less sex since splitting with Orlando last year.
She explained: "One thing I've noticed is now that I'm having less sex my body isn't as toned. The more sex I have, the more defined my arms and stomach get. Orlando and I always had great chemistry."
Miranda believes splitting from her spouse will benefit their son.
She added: "Two happy parents are better than two unhappy parents."

Rita Ora likes to run around naked at home.
The 'How We Do' hitmaker bought her first house last year after being kicked out of her rental property for making too much noise, and she's confessed that although she sometimes finds living alone "scary" she also enjoys it because it means she can strip off and run around naked.
She said: "I've just bought my first house and I'm beginning to realise what it's like being an adult and having to pay bills.
"Everything's scary when you live by yourself - even dark corners! I like playing music really loudly and running around naked though - it's my new favourite thing to do.
"I bet everybody does it. I love putting the heating on and not being cold, but being naked."
The 23-year-old star also opened up about her relationship with 'Under Control' hitmaker Calvin Harris, 30, who she's been dating for a year, and claims he can be annoying at times.
She told The Hits Radio's 'Breakfast with Darryl' show: "In all honesty, we have our separate lives. I'm a singer and Calvin's an amazing producer and DJ who plays all over the world.
"If you really want to make it work long distance you can. Thank God technology exists! It comes down to patience and trust really. We always make sure each of us is OK.
"I do get annoyed with him sometimes, I'm only human."