Martin Luther King Jr.'s granddaughter reflects 50 years after his assassination

Rev. Martin Luther King Jr.'s 9-year-old granddaughter said that if the civil rights leader was alive today, he would recognize that there is still work to be done in America.

"I think that he would be impressed about all the work that we're doing but we're not where we're supposed to be," Yolanda Renee King said today on "Good Morning America," on the 50th anniversary of her grandfather's assassination.

Yolanda, the eldest granddaughter of the civil rights icon, made her name known last month when she carried on King's legacy by speaking passionately about gun control at the March for Our Lives rally in Washington, D.C.

"My grandfather had a dream that his four little children would not be judged by the color of their skin but by the content of their character," Yolanda told a crowd of thousands. "I have a dream that enough is enough, and that this should be a gun free world, period."

Yolanda's mother, Arndrea Waters King, called it a "difficult" but "natural" decision to allow Yolanda to follow in her grandfather's activist footsteps.

"It was a bit difficult but because she has been so interested in the issue for so long and so passionate about it and wanted to do it, it was natural," Arndrea King said.

Yolanda and her parents, including Martin Luther King III, spoke to "GMA" from Memphis, where a huge crowd is expected to turn out at the Lorraine Motel, the site where Martin Luther King Jr. was killed on April 4, 1968.

Later today, bells will toll across the nation and prayers will be said as Americans of all colors and creeds pause to remember the life of the Nobel Peace Prize winner.

"I think he'd be disappointed with some of the discourse that we see [today] but he'd be very excited to see the high school student-led movements," Martin Luther King III said of his father. "He'd be very excited about the #MeToo movement. He'd be very excited about what Black Lives Matter is doing, all of these non-violent movements."

"He would know that we as a nation can, must and will do better," he added.

ABC News' Bill Hutchinson contributed to this report.