"They've had so much tragedy in the family that it's got to be hard for them to reconcile it all," says family biographer J. Randy Taraborrelli
PEOPLE Explains: All About Chappaquiddick, the Shocking Kennedy Scandal That Left One Woman Dead
Chappaquiddick is back in the national spotlight thanks to a new movie about the incident, due out in April. Find out more about what really happened that fateful night in 1969
In recent years, Kennedy and her golf cart have been a fixture at the parade
Ronald Reagan's Former Assistant Details His Final Years with Alzheimer's in New Memoir: 'It Was Heartbreaking'
Ronald Reagan's former executive assistant, Peggy Grande, is detailing her time with the late president in a new memoir, The President Will See You Now, out Feb. 21