Their union seemed like the outlier in the high-turnover world of Hollywood romances, built to withstand even the constant scrutiny of love in the limelight.
So when the news broke that Angelina Jolie (41) had called time on her decade-long union with Brad Pitt (52), fans were left reeling.
Even Angie's dad, actor Jon Voight, seemed to have no idea what prompted the out-of-the-blue bust-up.
Read more: Angelina Jolie files for divorce
“Something very serious must have happened for Angie to make a decision like this,” he told Inside Edition.
“I don’t know what (the reason) is,” he adds. “It’s a sad thing. Say a little prayer. I am concerned for Angie and the children and hopefully I will be seeing them very soon.”
Read more: Court documents: Angelina’s demands revealed
Brad's vague statement didn't offer much of an explanation and, aside from citing "irreconcilable differences" in court documents, Angie herself has remained mum.
PHOTO: Dan Jackman/WENN.com
So what could have prompted the shock split? The tabloids have their theories:
1. Brad was 'using drugs'
According to TMZ, the actress and activist Angie was "fed up" with her husband's abuse of "weed and possibly alcohol", and concerned about the effect it may be having on their six children.
As NYMag points out, this is not an entirely outrageous claim because in 2013, Brad revealed to Esquire magazine he had given up drugs to have a family.
“For a long time I thought I did too much damage – drug damage,” he said.
“I was a bit of a drifter. A guy who felt he grew up in something of a vacuum and wanted to see things, wanted to be inspired. I followed that other thing.”
2. Brad’s “parenting style” upset Angie.
Again, it was celeb gossip site TMZ citing “sources connected with the couple” who said that “Angelina’s decision to file has to do with the way Brad was parenting the children … she was extremely upset with his methods.”
While this may or may not be true, the fact that Angie has asked for full physical custody Maddox (15), Pax (12), Zahara (11), Shiloh (10) and twins Knox and Vivienne (8) certainly implies she isn't entirely happy about the idea of Brad taking the reigns.
She's offered her husband (and biological father of Shiloh and the twins) joint legal custody of their six children -- which means Brad will only get visitation rights.
Angie's lawyer Robert Offer said she made the decision "for the health of the family." Read into that what you will.
3. Brad has anger issues
The outlet also claims the actress and director feels Brad has “an anger problem,” which had become “dangerous for the children.”
4. Brad was having an affair -- and Angelina hired a PI who caught him in the act
According to Page Six, Angie believed Brad was "fooling around" with one of his co-stars -- which, given the circumstances under which they met (on the set of Mr & Mrs Smith in 2005, while Brad was still married to Jennifer Aniston), is not entirely unbelievable.
The outlet claims suspicious Angie hired a private detective -- who supposedly caught Brad in the act with his Allied co-star Marion Cotillard.
Brad and Marion on set on 6 May 2016. PHOTO: AW/WENN.com
"She hired a private eye because she felt that he was fooling around with her on the set, and it turns out, he was," the source said. "And that was the final straw."
But MailOnline quotes "a source close to Marion’s family in her home city of Paris", who said the 40-year-old actress is still dating fellow actor Guillaume Canet.
"Marion and Guillaume are blissfully happy, and these kind of claims are not what Marion wants to be hearing.
"Claims that she’s cheating on Guillaume with Brad will leave her absolutely devastated. This doesn’t sound like her at all."
Read more: ‘Saddened’ Brad speaks out on divorce as cheating rumours fly
5. There were Russian hookers involved...
Page Six's source also told the outlet: “The atmosphere [off the set of WWII drama Allied] was full of hard drugs and Russian hookers, and Angie was told Brad got caught up in it.
“He’s in the throes of some insane midlife crisis, and Angie is fed up.”
6. There was some sort of 'incident'
US Magazine Us Weekly has a source saying that the decision to divorce was as out-of-the-blue as it seems, made by Angie after some sort of major incident just days ago.
"The final divorce decision was only made one week ago," the insider said. "An incident took place and prompted [Angelina] to act and file."
While it's not clear what happened, it "affected the entire family," the source added.
Sources: NYMag, MailOnline, TMZ, US Weekly, Page Six