Kelly Clarkson's former husband and father of her two children, Brandon Blackstock, has passed away at the age of 48. Multiple outlets report that Blackstock, who also managed Clarkson's career, had been battling a terminal illness for some time.RELATED: Kelly Clarkson To Pay Brandon Blackstock More Than 1.3 Million And Monthly Child And Spousal SupportDetails On The Passing Of Kelly Clarkson's Ex HusbandOn Thursday, August 7, NBC News shared that Brandon Blackstock's representative confirmed his death after battling cancer for three years.