Brandon Blackstock's cause of death has been confirmed

He added to People: "Brandon Blackstock passed away peacefully at his home in Butte, Montana on August 7th under hospice care surrounded by his family."

Brandon - who had children River, 11, and Remy, nine, from his marriage to Kelly - died last week after battling cancer for over three years.

A statement from a family representative read: "It is with great sadness that we share the news that Brandon Blackstock has passed away.

"Brandon bravely battled cancer for more than three years. He passed away peacefully and was surrounded by family. We thank you for your thoughts and prayers and ask everyone to respect the family's privacy during this very difficult time."

Blackstock's passing came just a day after Kelly, 43, revealed that her ex-husband was ill and that she would be postponing the rest of her Las Vegas residency dates for August.

The Since U Been Gone hitmaker wrote on Instagram: "Unfortunately, I need to postpone the remainder of the August Studio Session dates in Las Vegas.

"While I normally keep my personal life private, this past year, my children's father has been ill and at this moment, I need to be fully present for them. I am sincerely sorry to everyone who bought tickets to the shows and I so appreciate your grace, kindness and understanding."

Kelly is understood to be "staying strong" for her kids in the wake of Brandon's death, even though the couple's marriage ended in acrimony.

A source told People: "Kelly and Brandon had their ups and downs, but at the end of the day, he was the father of her children and she is absolutely heartbroken for them. Her kids are her entire world, and she's staying strong for their sake."

The Because of You singer had always tried to remain "classy" for the sake of their kids after learning that Brandon - who served as her manager during their marriage - was seriously ill.

The insider added: "When she found out that he was sick, she remained protective of him for their sake.

"Kelly has always tried to keep things classy. It became clear earlier this year that Brandon was not doing well. She's been devastated for the kids."