Inside Loretta Lynn and Crystal Gayle's Sisterly Bond: We'd 'Have Our Words' Then 'We'd Laugh'

When Loretta Lynn and little sister Crystal Gayle posed for their joint PEOPLE cover story in 1978, they were two of country music's biggest stars. But behind the scenes, they were like any other siblings.

"I had brought two identical blouses that were different colors to the shoot, and I didn't know which one to wear. So, I was told which one I was going to wear!" Gayle recalled to PEOPLE last year. "That's what a big sister can do."

Gayle, now 71, added that she's always leaned on Lynn, who died at her home in Tennessee on Tuesday morning at the age of 90, for no-nonsense guidance.

"She got me my first recording contract [in 1970], and she told me the best advice: 'Don't sing anything that I would because we're only going to be compared,'" Gayle said. "She was right."

Ten years before Gayle got her recording contract, Lynn released her first single, "I'm a Honky Tonk Girl." A string of Top 10 hits — including "Don't Come Home A' Drinkin' (With Lovin' on Your Mind)," "You Ain't Woman Enough (To Take My Man)" and "Fist City" — followed, shooting her to international stardom.

Lynn's rags to riches story began in poverty-stricken Appalachia. The second eldest of eight children born to dad Melvin Webb, a coal miner who had black lung disease and died in 1959, and mom Clara in Butcher Hollow, Kentucky, Lynn was married at 15 to moonshine-runner Oliver "Mooney" Lynn Jr. and had four kids by the time she was 20.

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When Gayle (born Brenda Gail), the baby of the Webb family, arrived in 1951, Lynn and her husband had already moved away to Washington state, where Lynn first learned how to play and sing with a $17 Sears guitar.

Unlike her big sister, Gayle grew up in Wabash, Indiana, where their father had moved to a retired miners' colony and their mother had worked as a nurse's aide. She was the first of the Webb children to be born in a hospital.

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Though she had unsuccessfully tried to promote the music careers of two of her other siblings, Lynn tried again with Gayle, who spent her summers as a teenager touring with Lynn. Lynn even came up with Gayle's stage name, which was inspired by the South's Krystal hamburger chain.

At age 16, Gayle performed at the Grand Ole Opry in Lynn's place.

"Loretta was sick," Gayle told PEOPLE in 2016. "I know Mooney, her husband, talked somebody into letting me go on stage that night."

When Lynn wrote a tune for singer Brenda Lee titled "I've Cried (the Blue Right Out of My Eyes)," Gayle argued, "Lee's eyes are brown, so I got it." While the track was a modest hit for Gayle when it was released in 1970, it became one of her signature songs.

In the years that followed, Gayle's career continued to rise thanks to a string of elegant country-pop hits, including her 1977 single "Don't It Make My Brown Eyes Blue." With success of her own, Gayle was made out to be rivals with Lynn, particularly after she bested her big sister for CMA female vocalist in 1977.

Gayle unintentionally added fuel to the fire of falling-out rumors when she addressed how Lynn's husband helped nurture her early career during an interview.

"Mooney was taking me around to radio stations and getting me going," she said. "But some stupid woman remarked to Loretta that she should watch her baby sister. It only takes a seed of doubt. In the back of her mind I think she always thought, 'Hmmmmm."'

Despite the speculation, Gayle insisted in 2021 that there was never any bad blood.

"We're sisters, so of course we're going to have our words," she said, "but it was never anything major. We'd laugh about it and go on with our careers."

In 1978, Lynn said that the sibling rivalry was fabricated by people's imagination.

"We fight a little bit, but that's just sisters," she said. "And we never fight over the music business."

"Crystal has a style of her own," she added. "But I'm country and that's the way I'm gonna stay. It's fed me real good. If I tried to go pop, I couldn't make it."

At the time, Gayle said she also planned to avoid the grind that she'd seen wear down Lynn.

"I've learned from her mistakes," she said. "She never knows ahead of time what she's doing. When the time comes, she's told. I'm more my own boss. I've learned to say 'No."'

When Gayle released her album You Don't Know Me in 2019, she had Lynn and their sister Peggy Sue Webb Wright contribute their vocals on "Put It Off Until Tomorrow," a song co-written by Dolly Parton and Bill Owens in the mid-1960s. Lynn recorded her track at Gayle's Nashville studio just a few months before suffering a stroke in May 2017.

"It's very special that she would do it," Gayle told PEOPLE. "She came in and sang it, and said, 'What's next?' If I'd had 10 tracks done, she would have sung every one of them that day. I should have had more than one."

Though Gayle said in 2021 that she hadn't seen Lynn in "a while because [of the COVID-19 pandemic," she said she was "so proud and honored to be her sister."