Keough died in Calabasas, California, Roger Widynowski told CNN Sunday.
The representative said he did not have further details on the circumstances of Keough's death, including the date.
Presley is "entirely heartbroken, inconsolable and beyond devastated," Widynowski said in a statement, "but trying to stay strong for her 11 year old twins and her oldest daughter Riley."
"She adored that boy. He was the love of her life," Widynowski said.
Keough's father was the musician Danny Keough.