Everly, 74, suffered from chronic obstructive pulmonary disease, his wife, Patti, told the Los Angeles Times. She said his heavy smoking was responsible.
The Everly Brothers were popular in the early rock 'n' roll era with hits such as "Cathy's Clown," "All I Have To Do Is Dream" and "Walk Right Back." While their last record to make the Top 10 was "That's Old Fashioned" in 1962, they were an important influence on the Beatles, the Byrds and other groups.
Don and Phil Everly began performing as children with their father, Ike Everly, and mother, Margaret Embry. In the 1950s, as they switched to a duo, they got a hand from Chet Atkins, a longtime family friend.
Linda Ronstadt, who recorded Phil Everly's "When Will I Be Loved," said the two had "that sibling sound."
"The information of your DNA is carried in your voice, and you can get a sound that you never get with someone who's not blood related to you," Ronstadt said. "And they were both such good singers -- they were one of the foundations, one of the cornerstones of the new rock 'n' roll sound."
The brothers were inducted into the Rock 'N' Roll Hall of Fame in 1986, soon after it opened.
After a period of estrangement, the brothers reunited in 1983. They continued to perform and record occasionally until recently.
Phil Everly is survived by his wife, his brother, his mother, two sons and two granddaughters.
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