The only daughter of the late Senator Edward Kennedy, Kara Kennedy Allen, died suddenly Friday evening, NBC News has learned.
The 51-year-old mother of two teens died while at a health club in Washington, D.C.
Kennedy Allen had been a survivor of lung cancer and family friends say she had been in remission for a few years.
No further details about the circumstances of her death were available, but family members were told that a heart attack was suspected.
Kennedy Allen maintained a very private life. She made a public appearance at the White House on August 13, 2009, to accept the Medal of Freedom awarded to her father by President Obama.
In August 2009, her father lost his battle with brain cancer and she did a reading at the funeral as well.
A longtime resident of Maryland and the D.C.-area, she served on boards for family-related nonprofits and had previously worked as a television producer.
Kara Kennedy Allen is mother to Grace Kennedy Allen who turns 17 on Monday and Max Greathouse Allen, 15.
She is survived by her mother, Joan Kennedy, and younger brothers, Edward Kennedy, Jr., and Patrick Kennedy and their families.