Natalie Cole, the American pop and blues singer known for hits such as This Will Be, Unforgettable and Our Love, has died at age 65.

The daughter of Nat King Cole, she won nine Grammy Awards in a career that began in the 1970s. Her Unforgettable… with Love sold 30 million copies and won the Grammy for album of the year.

Cole had cancelled her appearances in December and into January after falling ill. She died at a Los Angeles hospital of congestive heart failure.

"Natalie fought a fierce, courageous battle, dying how she lived ... with dignity, strength and honour. Our beloved Mother and sister will be greatly missed and remain UNFORGETTABLE in our hearts forever," read the statement from her son, Robert Yancy, and sisters Timolin and Casey Cole.

Grammy Awards executive producer Ken Ehrlich said Cole had "one of those magical voices that grabbed you from the first note.

"It could sound like honey, but when she wanted to belt, she could keep up with the best of them. In a way, and not just in lineage, Natalie was the connector between the great singers of her father and Ella's generation, and the great female voices who were to dominate in the last 25 years," Ehrlich said in a statement.

Fellow singer Tony Bennett also recalled his relationship with both her father and her family.

"Natalie was an exceptional jazz singer and it was an honour to have recorded and performed with her on several occasions," he said.

Toronto jazz musician Alex Dean worked with Cole a few times when the singer visited the city, saying she was "wonderful" to work with.

"She always said that she felt most comfortable standing in front of a kick-ass big band; that is what she liked, that's where she felt the best," Dean said. "She was so wonderful and so great that you want to bring your A-game, you don't want to mess around — she gets the best you have."

Cole's early career in the 1970s with her band Black Magic disappointed club owners because she sang R&B and rock, rather than her father's jazz and contemporary song favourites.

She teamed up with writer-producer team Chuck Jackson and Marvin Yancy in 1973, who helped her to a string of R&B hits such as This Will Be (An Everlasting Love), Inseparable, I've Got Love on My Mind and Over You.

Move into pop

Her recording of Bruce Springsteen's Pink Cadillac in 1988 signaled a change of musical focus, as Cole made a series of albums that covered the same American pop standards as her father.

While making the album Unforgettable… with Love using tracks of her father's voice, Cole said she had to "throw out every R&B lick that I had ever learned and every pop trick I had ever learned. With him, the music was in the background and the voice was in the front."

"I didn't shed really any real tears until the album was over," Cole said. "Then I cried a whole lot. When we started the project it was a way of reconnecting with my dad. Then when we did the last song, I had to say goodbye again."

After the breakaway success of Unforgettable…With Love, she recorded Holly & Ivy and Stardust, touring with an orchestra led by Nelson Riddle, the same composer and arranger who worked with her father.

More recently she recorded Still Unforgettable in 2008, which won the Grammy for best traditional pop vocal album and The Most Wonderful Time of the Year in 2010, which she recorded for a PBS special with the Mormon Tabernacle Choir.

She was nominated for three Latin Grammy Awards in 2013 for her first Spanish-language album, Natalie Cole en Español.

Struggle with addictions

Cole made TV appearances on Grey's Anatomy and Touched by an Angel and performed her Something's Gotta Give  on American Idol in 2009.

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Singer Natalie Cole performs March 2, 2015, in New York. She has died at age 65. (Evan Agostini/Invision/Associated Press)

Throughout her life she struggled with drug addiction. In her 2000 autobiography, Angel on My Shoulder, Cole discussed how she had battled heroin, crack cocaine and alcohol addiction for many years. She spent six months in rehab in 1983.
 
When she announced in 2008 that she had been diagnosed with hepatitis C, a liver disease spread through contact with infected blood, she blamed her past intravenous drug use.

Cole received chemotherapy to treat the hepatitis and "within four months, I had kidney failure," she told CNN's Larry King in 2009. She needed dialysis three times a week until she received a donor kidney on May 18, 2009. The organ procurement agency One Legacy facilitated the donation from a family that had requested that their donor's organ go to Cole if it was a match.

"I think that I am a walking testimony to you can have scars," she told People magazine. "You can go through turbulent times and still have victory in your life."

She criticized The Recording Academy for giving five Grammys to drug user Amy Winehouse in 2008.

"I'm an ex-drug addict and I don't take that kind of stuff lightly," Cole explained at the 2009 Grammy Awards. Hepatitis C "stayed in my body for 25 years and it could still happen to this young woman or other addicts who are fooling around with drugs, especially needles."

Cole was married three times and is survived by a son, Robbie Yancy, by her first marriage to Marvin Yancy.
 

With files from the Associated Press