Brandon Blackstock learned of his cancer diagnosis following his divorce from Kelly Clarkson.

A source tells PEOPLE that Blackstock, who died on Aug. 7 at age 48, “was diagnosed after the divorce.” Blackstock and Clarkson, 43, were married in 2013 and welcomed their daughter, River, now 11, and son, Remington, now 9.

Seven years later, the singer-songwriter filed for divorce, citing irreconcilable differences. Their divorce was finalized two years later.

A second source tells PEOPLE Blackstock moved back to Montana in 2022 following his diagnosis.

A representative for Blackstock’s family announced his death in a statement shared with PEOPLE. “It is with great sadness that we share the news that Brandon Blackstock has passed away,” the statement read.

“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.”

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The day before Blackstock died, Clarkson postponed the August shows of her Las Vegas residency, revealing that Blackstock had been “ill” and she needed to be present for her children.

“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,” she wrote in a statement.

“I am sincerely sorry to everyone who bought tickets to the shows and I so appreciate your grace, kindness and understanding.”

A source told PEOPLE that Clarkson has “been devastated” for her children amid her ex-husband’s private illness.

“When she found out that he was sick, she remained protective of him for their sake,” the source said. “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.”

Clarkson and Blackstock’s divorce was acrimonious and involved several legal proceedings following the finalization. The American Idol winner knew how important the relationship her children, River and Remington, had with their father as, the source added.

“The divorce was incredibly difficult for her — messy, painful and something she felt terrible about,” the source said. “But she always wanted her kids to have the best relationship possible with their dad. She never spoke poorly about Brandon to the kids.”

Along with the children he shares with Clarkson, Blackstock was a father to son, Seth, and daughter, Savannah, from a previous marriage.