Kelly Clarkson continues to prioritize her two children after the death of their father, Brandon Blackstock.

A source tells PEOPLE that the singer-songwriter has “been devastated” for her kids River, 11, and Remington, 9, as their dad, who died on Thursday, Aug. 7 at age 48, faced cancer for three years privately.

“When she found out that he was sick, she remained protective of him for their sake,” the source says. “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, 43, filed for divorce from Blackstock, a talent manager, in 2020 after seven years of marriage, and their split was finalized two years later. Though their divorce was acrimonious, and the two were later involved in various legal proceedings, the source says that Clarkson knew the importance of her children’s relationship with their father.

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

In 2023, Clarkson opened up about co-parenting with Blackstock, and reiterated that her children and their feelings were her top priority.

“I ask my kids every night when we’re snuggling and I put them to bed, ‘Are you happy? And if you’re not, what could make you happier?’ ” Clarkson said on Angie Martinez’s IRL podcast. “Especially the past two years … it kills me [but] I want them to be honest so I don’t ever say, ‘Oh God, don’t tell me that,’ but a lot of times it would be like, ‘I’m just really sad. I wish Mommy and Daddy were in the same house.’ They’re really honest about it. I’m raising that kind of individual.”

She continued, “I just sit there and I’m like, ‘I get it. I’m from a divorced family as well. I get it. That sucks. But we’re going to work it out. And you are so loved by both of us.’ “

In 2021, Clarkson said on her talk show that sharing parenting duties was “tough,” but there were things she and Blackstock agreed on.

“It’s tough. … I know with me and Brandon, it’s just a difficult thing because we’re in different places, and it’s like, we both agree on the main things, but it’s a hard thing when you’re not together all the time, for me personally,” she said, later adding, “As long as you make sure it’s about the children and their best interests, then we’re both on board.”

A rep for the family announced Blackstock’s death on Aug. 7 in a statement that revealed he’d “bravely battled cancer for more than three years.”

“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.”

Blackstock had not publicly shared his diagnosis prior to his death, though Clarkson revealed that he was “ill” in a statement shared on Wednesday, Aug. 6.

Clarkson wrote on Instagram at the time that she would be postponing her Las Vegas residency in order to be “fully present” for her kids.

“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.”

The “Stronger” singer missed several episodes of her talk show, The Kelly Clarkson Show, earlier this year largely due to Blackstock’s illness, multiple sources told PEOPLE.