Dolly Parton is mourning the loss of her fellow female country music icon Loretta Lynn.

"So sorry to hear about my sister, friend Loretta,” Parton wrote on social media. “We've been like sisters all the years we've been in Nashville and she was a wonderful human being, wonderful talent, had millions of fans and I'm one of them. I miss her dearly as we all will. May she rest in peace."

Lynn’s family confirmed her death in a statement to CMT.

"Our precious mom, Loretta Lynn, passed away peacefully this morning, October 4th, in her sleep at home at her beloved ranch in Hurricane Mills," the statement said.

The women have similar backgrounds are they were both born into large families in Appalachia. Parton is from Sevierville, Tennessee, and Lynn grew up in Butcher Hollow, Kentucky. Parton released her first hit song in 1959 and Lynn’s came in 1960.  At 90 years old, Lynn was about 14 years older than Parton, but both women are singer/songwriters who are members of the Country Music Hall of Fame, The Grand Ole Opry and they are the first and second women respectively to win the Country Music Association’s coveted Entertainer of the Year Award. Lynn accepted the trophy in 1972 and Parton won earned the honor in 1978.

As a songwriter, Lynn crafted a persona of a defiantly tough woman, a contrast to the stereotypical image of most female country singers. The Country Music Hall of Famer wrote fearlessly about sex and love, cheating husbands, divorce, and birth control and sometimes got in trouble with radio programmers for material from which even rock performers once shied away.

Her biggest hits came in the 1960s and '70s, including "Coal Miner's Daughter," "You Ain't Woman Enough," "The Pill," "Don't Come Home a Drinkin' (With Lovin' on Your Mind)," "Rated X" and "You're Looking at Country."

In "Fist City," Lynn threatens a hair-pulling fistfight if another woman won't stay away from her man: "I'm here to tell you, gal, to lay off of my man/If you don't want to go to Fist City." That strong-willed but traditional country woman reappears in other Lynn songs. In "The Pill," a song about sex and birth control, Lynn writes about how she's sick of being trapped at home to take care of babies: "The feelin' good comes easy now/Since I've got the pill," she sang.

"It was what I wanted to hear and what I knew other women wanted to hear, too," Lynn told the AP in 2016. "I didn't write for the men; I wrote for us women. And the men loved it, too."

The Associated Press contributed to this report.