(CNN) -- If the Kennedys have helped define modern ambition and 20th century success, they've also withstood two generations of televised tears and premature farewells.

With little hope of finding John F. Kennedy Jr., his wife and her sister alive, Kennedy watchers were reminded of the twin clouds of controversy and tragedy that seem to perpetually surround America's most prominent political family.

There was, of course, the horrifying assassination of President John F. Kennedy. The hail of bullets, five years later, that killed the brother who aspired to the same office. The Chappaquiddick accident in 1969 that killed a young woman and virtually ensured that Ted Kennedy would never be president.

The list goes on. Joseph P. Kennedy Jr., the oldest son of Joseph and Rose Kennedy, died in a plane crash in 1944 during World War II. He was 29. Sister Rosemary Kennedy has been institutionalized since 1941 because of mental retardation and the effects of a failed lobotomy.

Kathleen Kennedy married William John Robert Cavendish, the Marquess of Hartington, who was killed in World War II. She later died in a plane crash in France in 1948. She was 28.

Joe and Rose took solace in their three surviving sons -- John, Robert and Edward -- but the family's tragic legacy followed them, too. And it didn't end there; it trailed their grandchildren.

Robert Kennedy's son David died in 1984 of a drug overdose in a hotel after being ousted from the family vacation home at Palm Beach. His other son, Joseph (Joe), was involved in a 1973 car accident that left a female passenger paralyzed for life. Now a Massachusetts congressman, Joe announced in 1997 he was abandoning plans to run for governor. The same year, his ex-wife wrote a book criticizing him for asking the Roman Catholic Church for an annulment.

Yet another son, Michael, who drew negative publicity for an alleged affair with his family's underage baby sitter, was killed on December 31, 1997, in a skiing accident in Aspen, Colorado. He was 39.

In 1969, aide Mary Jo Kopechne died when Edward Kennedy drove his car off a bridge on Chappaquiddick Island in Massachusetts

The clan's surviving patriarch, Sen. Edward M. Kennedy drove a car off a bridge on Massachusetts' Chappaquiddick Island in 1969 after a party. The accident killed aide Mary Jo Kopechne, and controversy over the incident effectively ended the Massachusetts Democrat's presidential aspirations.

His son Edward Jr. had his right leg amputated in 1973 because of cancer; his son Patrick, now a congressman, sought treatment for cocaine addiction as a teen-ager in 1986.

His nephew, William Kennedy Smith, was accused of rape in 1991 at the family estate in Palm Beach, Florida. He was acquitted.