Kelly Clarkson's ex-husband Brandon Blackstock has tragically passed away after battling cancer, and her number one focus is taking care of their kids.

"Kelly’s work schedule has been difficult over the last few months as she needed to take care of her kids," a source tells Us Weekly . " She needed the time off as her kids come first. It’s terrible and sad. Kelly is a great mom and has needed to be there for her kids. Only a few people in Kelly’s circle [and] a handful of her show’s team [were aware of] what was going on behind the scenes."

An insider also spoke to Page Six , saying "It’s been exhausting and so sad… Kelly has been working so hard, as well as looking after Brandon. Despite their difficult divorce, he’s still the man she loved and still her kids’ father."

A rep fo

See Full Page