TMZ reports Benjamin took his own life on Sunday in Calabasas, California.
In a statement to the website, Lisa’s manager, Roger Widynowsk, said: "She is completely heartbroken, inconsolable and beyond devastated 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."
The son of Danny Keough, Benjamin followed in his famous family’s footsteps and was also a musician. He also acted in a short film called Rod and Barry.
Benjamin kept quite a low profile, but was known to look almost identical to his famous grandfather.
“He does [look so much like Elvis]!” Lisa Marie told CMT in 2012. “He was at the Opry and was the quiet storm behind the stage. Everybody turned around and looked when he was over there. Everybody was grabbing him for a photo because it is just uncanny.”
Elvis’s daughter also admitted she’s “overwhelmed” at times at how much they look alike. As for whether Ben inherited his father’s musical skills, she has been cagey on behalf of her son.
“He’s doing his own thing right now,” she told Huffington Post in 2013. “I’m going to let him decide when he wants to go out and do what he wants to do.”
Lisa, who has previously opened up about her addiction to opioids and painkillers, said her children were the reason she was able to recover.
In a foreword she wrote for the book The United States of Opioids: A Prescription for Liberating a Nation in Pain by Harry Nelson, she said: “As I write this, I think of my four children, who gave me the purpose to heal,” and that made her think of “the countless parents who have lost children to opioids and other drugs.”
She ended by saying that she is “grateful to be alive today” and especially appreciative “to have four beautiful children who have given me a sense of purpose that has carried me through dark times.”
Benjamin has three sisters, Riley Keough, 31, and twins Finley and Harper Lockwood, 11.
Fans have flooded Lisa Marie’s Instagram comments with their condolences.
Additional reporting by Taryn Ryder.