No official announcement had been made regarding cause of death, but The (White Plains, N.Y.) Journal News -- citing a source close to the investigation into her death -- reported Kennedy, 52, hanged herself. An autopsy was scheduled for Thursday.
An architect and designer, Kennedy married the son of the late U.S. Sen. Robert F. Kennedy, D-N.Y., in 1994. The couple were the parents of four children.
She had a history of alcohol abuse, including a May 2010 incident in which she called police to her home. Kennedy told officers her husband had been "verbally abusive to her and her children," but police officers said she appeared "visibly intoxicated" and "had great difficulty collecting her thoughts and articulating her reasons for calling," the newspaper said.
Robert F. Kennedy Jr. filed for divorce two days later, and police were called to the home the day after that when he told officers she was intoxicated, the newspaper said, citing official documents. She was charged with driving while intoxicated a few days later, and later pleaded guilty to driving while impaired, the report said.
She was arrested again Aug. 21, 2010, on charges of driving while impaired by prescription drugs. That case was dismissed.
"We deeply regret the death of our beloved sister Mary, whose radiant and creative spirit will be sorely missed by those who loved her," CNN reported her family said in a statement. "Our heart goes out to her children, who she loved without reservation."