Natalie Cole's family revealed that the late singer's death on Dec. 31 was caused by idiopathic pulmonary arterial hypertension, which ultimately led to heart failure.

As Breaking Celebrity News reported, Cole passed away at age 65 in a Los Angeles hospital, just before the New Year arrived.

In a statement to the Associated Press, Cole's family shared that when the "Unforgettable" singer underwent a kidney transplant in 2009 after struggling with problems related to Hepatitis C, s