ATLANTA – Yolanda King, the firstborn child of the first family of the civil rights movement who honored that legacy through acting and advocacy, died late May 15. She was 51.

The daughter of the Rev. Martin Luther King Jr. and Coretta Scott King died in Santa Monica, Calif. Family members did not know the cause of death, but suspect it might have been a heart problem.

“This is just the last thing and the last person that we expected this to happen to,” said Issac Newton Farris, the Kings’ cousin and CEO of the King Center. “At least with my aunt [Coretta Scott King], we had some warning. Yolanda as far as we knew was healthy and certainly happy.”

Former Mayor Andrew Young, a lieutenant of her father’s who has remained close to the family, said King was going to her brother Dexter’s home when she collapsed in the doorway. Farris said she died near Dexter King but would not elaborate.

Yolanda King, who lived in California, appeared in numerous films, including “Ghosts of Mississippi,” and played Rosa Parks in the 1978 miniseries “King.” She also ran a production company.

“She was an actress, author, producer, advocate for peace and nonviolence, who was known and loved for her motivational and inspirational contributions to society,” the King family said in a statement.

“She used her acting ability to dramatize the essence of the movement,” said Rep. John Lewis, D-Ga., who worked alongside King’s father. “She could motivate and inspire and tell the story. I heard her recite ‘I Have A Dream’ on several occasions. She made it real, made it part of her. I think her father would’ve been very, very proud of her.”

Yolanda King participated in the University of Maine’s celebration of Black History Month in February 1995. Billed as a lecture, her presentation in Orono on the history of civil rights was infused with poetry, dramatic characters and storytelling.

King described how the movement was launched by a weary Rosa Parks who refused to move to the back of the bus, the bus boycott led by her father and others that lasted for 381 days and brought the Montgomery, Ala., bus system to its knees, and sit-ins, protests and marches.

King also spoke at the University of Southern Maine in February 1997, and she also spoke before a crowd of several hundred at an NAACP breakfast in Portland on Jan. 19, 1998, urging continued support of affirmative action programs around the country.