Keith Urban Marks Daughters 18th Birthday Apart from Nicole

is set to celebrate daughter 's milestone 18th birthday without ex-wife , as the former couple continue navigating life after their split.

The country music superstar, 58, will reunite with Sunday and her younger sister Faith Margaret, 15, for a private birthday lunch before jetting off to to headline Country Night at the Lakefront Music Fest, according to New Idea.

Nicole, 59, is not expected to attend the intimate family gathering, although the publication claims Keith has been invited to Sunday's larger birthday party later that day.

'It's still a little too raw for Nicole and Keith to be sitting at the same dinner table, but he is invited to Sunday's party,' an insider told the magazine.

'Rather than make things uncomfortable, he's going to have lunch with her and Faith to celebrate before he heads to the Lakefront Music Fest.'

The reported birthday plans mark a significant moment for Keith, who has largely kept a low profile with his daughters since news of his split from Nicole emerged in September last year.

Despite celebrating separately, the publication claims the former couple have settled into a more united co-parenting arrangement as they put their daughters first.

The reported celebrations come as Nicole shared a heartfelt public tribute to Sunday on Instagram to mark her daughter's milestone birthday.

The Oscar-winning actress posted a series of family photographs alongside the caption: 'Happy Birthday our beautiful Sunday Rose. We love you so much.'

Sunday has increasingly stepped into the spotlight in recent years after launching a modelling career at just 16.

While her runway debut sparked online criticism, with some branding her a 'nepo baby' and mocking her walk, the teenager has continued to carve out a name for herself in fashion.

Just this week, she returned to the runway for Dior during Paris Fashion Week, further cementing her place in the industry.

She brushed off the blowback and soldiered ahead with her career, parading down her latest catwalk this Monday for the Dior show at .

One day later, she reached her majority and received a glowing Instagram tribute from her mother, who wrote: 'Happy 18th my angel, you couldn't be more loved.'