WASHINGTON (REUTERS) - Grammy-winning singer Natalie Cole, whose biggest hit came in a virtual duet with her late father, pop legend Nat King Cole, of his decaces-old hit Unforgettable has died at the age of 65, her family said on Friday.

The family's statement said Cole died Thursday night at Cedars-Sinai Hospital in Los Angeles from "ongoing health issues."

Cole's career spanned five decades in the R&B, soul, jazz and pop genres. In 2015 she had cancelled appearances citing medical reasons.

The TMZ celebrity news website said Cole, who had struggled in the past with drugs, died from congestive heart failure following complications from a kidney transplant and hepatitis C, diagnosed in 2008.

"It is with heavy hearts that we bring to you all the news of our Mother and sister's passing," the Cole family statement said.

"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 remains UNFORGETTABLE in our hearts forever."

Cole broke out in 1975 with the hit This Will Be, which won the Grammy for best R&B female performance and also earned her the Grammy for best new artist.

Critics compared her to Diana Ross and Aretha Franklin, but her career floundered in the 1980s when she ran into problems with heroin.

She bounced back, and her career reached the superstar level in 1991 when she recorded Unforgettable ... With Love. The album contained songs associated with her father, the silky-voiced singer who was one of the most popular performers of the 1940s and 1950s but who died before his daughter began her solo career.

Using technology that was cutting edge at the time, studio engineers merged her voice with her father's in the song Unforgettable, which had been a hit for Nat King Cole in 1951. The result was a moving, sentimental No. 1 hit 40 years later, that actually sounded as if the two were singing a duet.

The song, and the album it came from earned Cole three Grammy Awards.

"I thank my dad for leaving me such a wonderful, wonderful heritage," Cole said in accepting her awards.

Her other hits included Everlasting, Sophisticated Lady, I've Got Love On My Mind, and Good To Be Back.

In all, Cole won nine Grammys.

The success of Unforgettable capped her comeback after a dark period of heroin addiction. In Angel On My Shoulder, her 2000 memoir, Cole said she turned to drugs because of unresolved issues in her life, including being molested as a child and her father's death when she was 15.

Cole was diagnosed with hepatitis in 2008 from sharing needles with drug addicts, and underwent kidney transplant surgery in 2009. This past autumn, she cancelled several concerts that had been scheduled for November and December, citing a recent medical procedure.

Her 2008 album of pop standards, Still Unforgettable, included another duet with her father, Walkin' My Baby Back Home.

Her most recent work was 2013's Natalie Cole en Espanol.

Cole portrayed herself in Livin' For Love: The Natalie Cole Story, a 2000 television movie that depicted her drug addiction.

"We've lost a wonderful, highly cherished artist and our heartfelt condolences go out to Natalie's family, friends, her many collaborators, as well as to all who have been entertained by her exceptional talent," Neil Portnow, president of the Recording Academy, said in a statement.

"#NatalieCole, sister beloved & of substance and sound. May her soul rest in peace. #Inseperable," the Reverend Jessie Jackson posted on Twitter.

"#NatalieCole.. Condolences to family. What an incredible woman, a loving. joyful & peaceful soul. Rest in peace," Democratic strategist Donna Brazile said in another tweet.

Cole was married three times.