U.S. President Joe Biden joined former Democratic presidents and others to honor longtime human rights advocate and storied political family matriarch Ethel Kennedy at a memorial service in Washington on Wednesday after her death last week at age 96.

The widow of Robert F. Kennedy — a former U.S. attorney general and U.S. senator, who was assassinated while seeking the Democratic presidential nomination in 1968 — founded a human rights center to carry on her husband's work.

She never remarried and went on to raise her 11 children, enduring a host of other family tragedies along the way, including separate plane crashes that killed her parents, brother and nephew, as well as the untimely deaths of several of her children, grandchildren and a great-grandchild.

She and her husband were devastated by the assassination of his brother, President John F. Kennedy, in Dallas in 1963.

Biden, a fellow Irish Catholic who has leaned on his faith amid his own losses, including the death of his son Beau, said the Democratic family matriarch was there for him at his time of tragedy. He said her husband had been one of his heroes.

"Ethel was a hero in her own right," Biden said in remarks at the Cathedral of St. Matthew the Apostle in Washington, just blocks from the White House.

Former Democratic presidents Bill Clinton and Barack Obama, as well as former House Speaker Nancy Pelosi and others, also reflected on her life.

The son of civil rights leader Martin Luther King Jr., who was assassinated just two months before Robert Kennedy, noted the two families' shared journey and understanding of sacrifice amid their work for social justice.

"Faith and history knitted us together. Respect and love has kept us together," Martin Luther King III told the crowd.

The Kennedys were known for their parties and Wednesday's service was no different, with scores of relatives filling the pews and high-profile attendees remembering the infectious spirit highlighted by her children and grandchildren.

"She was a spitfire," Obama said. "As serious as Ethel was about righting wrongs, she never seemed to take herself too seriously."

Other Democratic attendees included California Governor Gavin Newsom and former top U.S. diplomat and presidential candidate John Kerry. Country star Kenny Chesney sang "You Are My Sunshine" while Sting surprised guests with "Fragile" and Stevie Wonder with "Isn't She Lovely."

Over the decades, Kennedy took up many causes championed by her late husband, including fighting poverty, working for social justice and protecting the environment. Obama awarded her the Presidential Medal of Freedom in 2014. She died on October 10 from complications following a stroke, her family said.

Her daughter Kathleen Kennedy Townsend was Maryland's lieutenant governor, while her son Joseph P. Kennedy II represented Massachusetts in the U.S. House of Representatives. Her grandson, former U.S. Representative Joseph P. Kennedy III, serves as special envoy to Northern Ireland.

Her son Robert F. Kennedy Jr., an anti-vaccine advocate and former independent presidential candidate, broke from his family's long Democratic ties to endorse Donald Trump in November's election.

Many members of the Kennedy clan have denounced his election politics and backed the Democratic ticket, now led by U.S. Vice President Kamala Harris after Biden stepped aside in July. Robert F. Kennedy Jr. attended Wednesday's service alongside his family but made no remarks.