Kelly Clarkson's "staying strong" but is "heartbroken" for her kids after ex Brandon Blackstock's death, a source tells PEOPLE. The singer and her late ex-husband share daughter River, 11, and son Remington,

Kelly Clarkson's ex husband and father of her two children, Brandon Blackstock, has died, and the family's loss makes their last Instagram posts even sadder.

The family of Kelly Clarkson’s ex-husband, Brandon Blackstock, is beginning to speak out after his tragic death at age 48. Brandon died on Thursday, August 7, after a private, yearslong battle with cancer. His brother, race car driver Shelby Blackstock, 35, was one of the first in the family to publicly address his passing.