Nicole Kidman's divorce from Keith Urban sent shockwaves through Hollywood. 

And now insiders have claimed that they know the real reason the A-list couple has parted ways - Urban is having a 'midlife crisis'. 

Urban, 58, has been 'acting out' RadarOnline reported this week, and has made a 'string of confusing choices' according to sources. 

The publication reports Urban had felt hemmed-in by his marriage and his frustrations resulted in the pair's split.

As the dust settles on the couple's divorce filing in Nashville, another insider has revealed the extent to which the country singer blindsided his actress wife.

Kidman and Urban had been experiencing marital difficulties but were 'getting it back together' when he floored her with the decision that it was all over, according to a source who has known the Australian actress for decades.

The Eyes Wide Shut star, 58, would be willing to patch things up - so long as Keith hasn't already moved on.

'She would get back with him in a heartbeat,' said the confidante.

Those within Nicole's inner circle believe that by the time TMZ broke news of the couple's separation on September 30, Keith was 'done' with the marriage.

At the time, reports indicated Nicole was 'blindsided' by the break-up. 

However, it was the Oscar-winner who filed divorce papers, citing 'irreconcilable differences'.  

Nicole shares daughters Sunday Rose, 17, and Faith Margaret, 14, with her country singer ex-husband.

It was revealed in September they had gone their separate ways.

While the Oscar winner is in a 'good headspace' as she moves on, the estranged couple have also been facing challenges.

'The hardest part is navigating the dynamic with their daughters,' a source told Us Weekly.

'The last thing Nicole wanted was a broken family,' the insider added before further expressing that she 'raised her daughters to be strong and is leading by example for them'.

The insider told the outlet that the star 'isn't necessarily trying to find her new normal throughout all of this, because they had been quietly separated for a while now'.

It was also revealed that, 'this next chapter feels more like a transition than a shock'.

According to divorce documents previously obtained by the Daily Mail, Nicole will become the primary residential parent of their two teenage daughters.

The estranged couple have agreed to an unusual parenting plan in which Nicole gets 306 days while Keith receives just 59 with their kids.