Luke Bryan's sister Kelly died suddenly in 2007, and the family has remained very quiet about the reason why.

Kelly was a 39-year-old mother of three when she died unexpectedly at home. The Bryan family has never really shared what happened until now. During an interview with Anderson Cooper on CNN's All There Is podcast, Luke said that many people felt that they were trying to cover something up, but that was not the case. After multiple autopsies, coroners couldn't find any reason was Kelly died that day. "There is a very, very small percentage of people that die for no reason in the world," Luke explains. "It's called sudden death syndrome." He added that her death was like "somebody just turned the switch off on her." He wishes another adult had been in the home that day, and wonders if that would have improved her chances of surviving. "She was everything in our lives. She was a mother of three children, and she was, I mean, the best mother you could ever dream of. And we all leaned on her for so many things," he says.