The Everly Brothers were, quite simply, one of the most influential groups in the history of popular music.
Their close, expressive vocals set the standard for any rock band that employed harmony as a primary feature - from The Hollies to the Beach Boys.
At the height of their popularity in the late 1950s and early 1960s, they scored 28 hits in the UK and were among the first 10 performers inducted into the Rock and Roll Hall of Fame when it opened in 1986.
Simon and Garfunkel recorded versions of their songs Bye Bye Love and Wake Up Little Susie, while The Beatles once toyed with calling themselves The Foreverly Brothers.
"They had that sibling sound," said Linda Ronstadt, who recorded a hit version of the band's When Will I Be Loved in 1975.
"The information of your DNA is carried in your voice, and you can get a sound [with family] that you never get with someone who's not blood-related to you.
"And they were both such good singers - they were one of the foundations, one of the cornerstones of the new rock'n'roll sound."
Don and Phil Everly were barely more than boys when they scored their first hit in 1957, but by that time they were already seasoned stage performers.
Schooled by their guitarist father, Ike, Phil made his live debut aged six. He was "too little to sing", Ike recalled, "so he would tell jokes".
Eventually, the boys were persuaded to work on their harmonies by the promise of a bicycle each.
"We all got to singing, and we had a little home-recording machine," Ike said in 1958. "It used to be that Don and Phil would give up their playing to come in and practise and practise."
By the age of 10, the brothers were performing on the family's radio show in Iowa, where they excelled at the close-harmony styles of Appalachian country singers such as the Blue Sky Boys.
Phil recalled their greatest influences as "traditional southern brothers' singing acts" like The Delmore Brothers - but Don, his elder by two years, found himself entranced by the raw power of rhythm and blues.
"The first time I heard the song Bo Diddley in 1955, it just nailed me," he told the BMI's Dave Simons last year.
"I remember thinking, 'I'll never be able to have that type of rhythm in any kind of country music.'"
But that's exactly what the Everly Brothers did.
Bye Bye Love, their debut single, was a straightforward rockabilly song until Don added a driving Bo Diddley beat below the melody.
They were rewarded with an instant number one on the US country charts - something the duo had never expected.
"We had no idea it was really going to make a difference, and we actually were glad to be recording anything," Phil told BBC Radio One in 2002.
"I was happy to make the $64 that we got for recording."
Indeed, Bye Bye Love, written by husband-and-wife team Felice and Boudleaux Bryant, had been turned down by 30 other artists before it was offered to the newcomers - and even they were unsure about it.
"There was so much anti-rock sentiment when we started out that we just didn't know what was going to happen," said Phil, speaking to Virginia's Freelance Star newspaper in 1995.
"We were told not to throw away our soap and towels because you never knew when you'd be back at the carwash."
The success of Bye Bye Love came when Phil - the younger brother - was just 18, but the band were almost instantly sent out on the road, joining package tours with the likes of Eddie Cochran, The Drifters, Jerry Lee Lewis, Bill Haley and Buddy Holly.
"It was like coming into college," Phil later recalled. "Everybody was a contemporary, it was like being in a fraternity. It was the best of times - I call it the golden age of rock."
But there was tension in the recording studio, where the brothers were under pressure to follow up the success of their debut.
"We must have listened to about 200 songs before Felice and Boudleaux Bryant came up with this," said Phil, referring to Wake Up Little Susie.
Although it was banned by some radio stations for its suggestive lyrics, Wake Up Little Susie gave the band another number one, and triggered a three-year run of classic pop hits, including All I Have to Do Is Dream, Bird Dog, 'Til I Kissed You, and When Will I Be Loved.
Perhaps their biggest hit was Cathy's Clown, which sold two million copies in the US. Written by Don and Phil together, it was inspired by Ferde Grofe's Grand Canyon Suite.
A UK number one in 1960, Cathy's Clown was a major influence on The Beatles - who copied the vocal arrangement for their single Please Please Me.
Indeed, Lennon and McCartney were seasoned Everly Brothers impersonators from their days in Hamburg - Lennon playing the role of Don, taking the lower, baritone parts, while McCartney aped Phil with his higher countermelody.
It wasn't just The Beatles, though. Dozens of the "British Invasion" bands were indebted to Don and Phil - who repaid the favour by recording an album with The Hollies, and incorporating jangling Beatles-style guitars into their own music.
But by the Summer Of Love, the brothers were overtaken by the new wave of rock, and their hits largely dried up.
They continued to make groundbreaking music, however, most notably 1968's sophisticated, sentimental Roots album.
The duo's career came to an abrupt halt when, in 1973, during the first of three scheduled shows at California's Knotts Berry Farm, Phil smashed his guitar and stormed off stage.
The following night, Don appeared alone and told the audience, "The Everly Brothers died 10 years ago."
The siblings barely spoke for a decade, making one exception to attend their father's funeral.
Despite later rapprochements and collaborations, the bust-up spelled the end of the band as a creative force.
The brothers' last high-profile concerts took place a decade ago, but their influence can still be felt today.
As recently as last November, Green Day's Billie Joe Armstrong and Norah Jones recorded a tribute to the brothers.
And Smiths guitarist Johnny Marr says he learned about the power of music as a child, watching his mother and aunt "breathlessly rushing into the house having bought the Everly Brothers' record Walk Right Back and watching them play it 15 times in a row, stood up at the record player."
Looking back in 1986 at the Everly Brothers' heyday, Phil said he was aware of their place in rock history.
"I think we helped lean the industry towards multiple groups," he told the Miami News.
"We weren't a doo-wah group from New York. We were like two people. But up until then it had been mostly teen idols."
But, modest to the last, he refused the tag of music legend.
"You still have to drive the child to school and make sure his lunch is packed," he said. "Everybody does that."