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Aretha Franklin lend her powerful voice not only to music — she also used it to speak out on behalf of the civil rights movement.

Franklin's father, Detroit Rev. Clarence LaVaughn (C.L.), was a close friend and colleague of Martin Luther King Jr., among various other icons in the civil rights era.

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The two men attended demonstrations together often, including a freedom march that took place months before the famed 1963 March on Washington, according to The Washington Post. In a 2009 interview with the newspaper, Franklin recalled King sleeping over at her dad's house whenever he made a pit stop in Detroit.

Eventually, a teenage Franklin joined King's civil rights tour across the U.S.

ARETHA FRANKLIN, 'QUEEN OF SOUL,' DEAD AT 76

“I asked my dad if it would be OK if I went [on the tour with King]," Franklin once recalled to the Post. “He said if that’s what I wanted to do, he thought it would be OK, so I went out for a number of dates with Dr. King. Harry Belafonte came out and of course, Andrew Young was there and Jesse [Jackson] came in and out.”

The pair grew close. Like the rest of the nation, Franklin was devastated by King's 1968 assasination in Memphis, Tenn. To honor her mentor and civil rights icon, Franklin volunteered to sing at his funeral.

Now, five decades later, one of King's kids is paying tribute to Franklin, who died on Aug. 16 at the age of 76 in her Detroit home.

"We were blessed to live in a world with #ArethaFranklin. Beyond her tremendous singing voice, she was a voice in the Civil Rights Movement. An instrument..." King's youngest daughter, Bernice, tweeted.

She continued, "Just as they welcomed #ArethaFranklin to their hearts during their lifetime, both my father and mother have welcomed the #QueenOfSoul to their heavenly home. #RIPQueen."

King's oldest son, Martin Luther King III, also shared his grief over Franklin's death.

"I am deeply saddened by the passing of Aretha Franklin. She was beyond a legend in the nation and world. I will always be grateful for her support of my father and the civil rights movement through the years. My prayers go out to her family and friends. Rest in Peace. #Respect," he wrote.