The Australian couple - who are parents to Sunday Rose and Faith Margaret - haven't shied away from opening up about their relationship in the past.
Last year, Keith released the song "Gemini," which revealed intimate details about their private life.
"She’s a maniac in the bed, but a brainiac in the head," the 51-year-old sings of the actress in the song.
Last month, Life & Style reported that the lovebirds were at "breaking point" and are "struggling to save their 13-year marriage."
"Nicole and Keith have some major issues and their marriage is on shaky ground," an insider allegedly told Life & Style.
"Their marriage is like a roller coaster and it’s been a living hell lately," they continued.
Arguments between the pair allegedly began when Keith insisted he had to return to the US early after the couple flew to Australia to spend their holidays with the family.
"Nicole accused him of rushing back to be around his young musician friends, specifically female ones," the insider claimed.
The publication also claimed that their relationship continued to suffer when Nicole was filming Big Little Lies as they hardly spent any time together.
"In some ways, it was like they were leading separate lives. The lack of communication led to trust issues and the trust issues led to fights," the source added.
The fighting has been so bad that friends "fear they’re at a crossroads."
"Nicole and Keith have had trial separations before, but nothing changes… it becomes more of a struggle to stay together. They might not be able to do it anymore."
However, Nicole's recent Instagram post revealed that their love is stronger than ever.