EXCLUSIVE: Natalie Cole's Sisters Open Up About Their Last Days With the Legendary Singer

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Following Natalie Cole's death, ET sat down with her sisters Timolin and Casey, who revealed why their sister suffered in secret.

The legendary singer was embattled with health issues for years before dying from congestive heart failure on Dec. 31 in a Los Angeles hospital, but kept silent about her illnesses. Casey told ET that Natalie treasured her privacy and didn't want to draw too much attention.

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"She was very protective of her family and her close friends, and I don't think that she wanted people to start feeling sorry for her," Casey said. "She really thought and prayed that she would overcome this."

The "Unforgettable" singer wowed the world with her talent, winning multiple GRAMMYs in her career, but she also had a drug-addled past. In 2007, she was diagnosed with Hepatitis C and had a kidney transplant in 2009.

Following the kidney transplant, Natalie began to experience complications with her heart and her siblings told ET that they knew this Christmas would be her last.

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"When we came to the hospital and spent Christmas Eve with her it was a godsend," Timolin said. "We were very blessed and thankful to spend that very special day with her that she loved. It was her favorite time of year."

Natalie is survived by her 38-year-old son, Robert Yancy, who Timolin says was "very close" to his mom.

"He is having a hard time," she said. "I think it's going to be a process."

Natalie's family is keeping her spirit alive through the Nat King Cole Generation Hope organization, which provides music education to children in need.

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Former ET host Mary Hart helped remember Natalie by reflecting on the time she spent with her in 2008, when Natalie was still in need of a new kidney.

"I'm a survivor," Natalie said at the time. "I don't know where I really got it from, but I just don't believe in giving up until the fat lady sings, and the fat lady hasn't sung yet."