Patrick Kennedy, younger son of the late Senator Edward Kennedy, was set to marry on Friday in a small private ceremony at the family's famous waterfront compound on Cape Cod in Massachusetts.
Kennedy, who turned 44 this week, will marry New Jersey school teacher Amy Petitgout, 32.
It will be the first marriage for Kennedy, who retired this year after 16 years representing Rhode Island in the U.S. House of Representatives.
The groom, smiling widely, went sailing Friday morning near the Hyannis Port property with his brother, Edward Kennedy Jnr, and other relatives and friends before getting ready for the ceremony, due to be presided over by Supreme Court Justice Stephen Breyer.
Kennedy told local reporters he felt "lucky" to be able to share the day with his family and bride, and felt that his late father would play a big role in the day's events.
Petitgout and Kennedy met last year when Kennedy was in New Jersey speaking about his aunt Eunice Kennedy Shriver's work with the Special Olympics.
Edward Kennedy died of brain cancer two years ago after more than four decades in the Senate. Patrick Kennedy's uncles were President John F. Kennedy and Senator Robert Kennedy, both of whom were assassinated in the 1960s.
While in Congress, Kennedy sought help in 2006 for dependency on prescription drugs after crashing his car into a security barrier in Washington.
Kennedy is now a visiting fellow at the Institute for Brain Science at Brown University in Providence, Rhode Island, and is an advocate for neurological research and mental health care.