Phil Everly had died at the age of 74.
The singer and musician was one half of pop duo the Everly Brothers alongside older brother Don.
The singer was a lifelong smoker and died of chronic obstructive pulmonary disease at a hospital in Burbank, California says his son Jason, reports British newspaper the Telegraph.
Wife Patti is devastated at the loss.
“We are absolutely heartbroken. He fought long and hard,” Patti told the Los Angeles Times.
The Everly Brothers were one of the biggest pop acts of the 1950s and early 1960s.
Hit songs included Wake Up Little Suzi, Bye Bye Love and All I Have to Do Is Dream.
They were elected into the Rock "n" Roll Hall of Fame in its first year, 1986, and were given a lifetime achievement award at the Grammys in 1997.
"It"s a terrible, terrible loss - for me, for everybody," US rock pioneer Duane Eddy, told BBC Radio 5live.
Rolling Stone magazine calls the Everly Brothers "the most important vocal duo in rock".
Their career spanned five decades, but Phil and Don performed separately for a decade from 1973 following an onstage breakup.
But the pair made up, and their relationship survived the feud.
"Don and I are infamous for our split but we"re closer than most brothers,” Phil previously told Time magazine.