Nicole Kidman and Keith Urban shocked fans on Monday when it emerged they had split after 19 years of marriage.

But the Oscar winner, 58, and the 57-year-old musician’s separation wasn’t a secret to their close friends, who reportedly knew the split was ‘inevitable’.

According to People, Nicole and Keith’s inner circle have known about the pair living separate lives ‘for a while’.

‘It really hasn’t been a secret that they’ve been living separately for a while now,’ a source told the publication.

‘People close to Keith felt like the split was kind of inevitable.’

The actress and musician’s separation was confirmed by the Daily Mail on Monday, with the couple ending their almost two decades of marriage.

Nicole Kidman and Keith Urban (pictured) shocked fans on Monday when it emerged they had split after 19 years of marriage

Nicole filed for divorce on Tuesday – citing irreconcilable differences.

A source claimed to the Daily Mail that there is speculation that Keith has already moved on with a younger woman in the music industry.

Daily Mail has contacted representatives for Nicole Kidman and Keith Urban for comment and has yet to hear back.

The former couple share daughters Sunday Rose, 17, and Faith Margaret, 14.

Nicole was previously married to Tom Cruise, 63, for 11 years from 1990 to 2001. They adopted two children together: Isabella, 32, and Connor, 30.

At this time, Keith — who is renting a home in Music City — is reportedly showing no interest in reconciling.

Those close to Nicole say that even the suggestion that he may be seeing someone else has been difficult for her to process.

Nicole and Keith were last seen together publicly in June, when they attended a FIFA World Cup match in Nashville, Tennessee.

According to People, Nicole and Keith’s inner circle have known about the pair living separate lives ‘for a while’

The country star has been away for much of the year on his High and Alive World Tour. He is due to perform in Hershey, Pennsylvania on Thursday.

Nicole and the children, meanwhile, have remained in Nashville, where the couple own a $4million compound.

In July, Keith dropped a hint that all was not well between the pair when he dramatically hung up during a phone interview with a radio station after a crude question about Nicole’s raunchy recent scenes, such as in her movies Babygirl and A Family Affair.

For her part, and while promoting her Netflix series The Perfect Couple in September last year, Nicole admitted there was no such thing as a ‘perfect’ marriage.

‘There’s no perfect anything,’ she said.

‘Anything that’s presented as perfect… forget it.’