Now, five decades later, one of King's kids is paying tribute to Franklin, who died on August 16 at the age of 76 in her Detroit home.
All week, tributes from fans and celebrities had been pouring in on social media.
King was a frequent guest in her father's home.
Aretha's health problems began in 2010. Her legendary voice, striking soul and undeniable talent had staying power, as she continued to perform up until 2017. There had also been reports that she suffered from diabetes, though it was unclear if she had type 1 or type 2.
Perhaps her most breathtaking performance took place at the 1998 Grammy Awards, when Franklin was called upon to fill in for an ailing Luciano Pavarotti and deliver the stirring aria "Nessun Dorma" from Puccini's Turandot.
Though LaBelle released a statement on Twitter acknowledging Franklin's passing, the two had a legendarily contentious relationship, which was well documented in interviews over the years, further complicating the possibility that evidence might exist of the two singers performing or appearing together in any capacity on the evening in question.
Watch her iconic performance above.
Civil rights leader and Congressman John Lewis said what made Franklin so great was "her capacity to live what she sang".
Franklin was born in Memphis, Tennessee, on March 25, 1942.
She sang for presidents and the pope.
Sir Elton added, on Instagram: 'Her voice was unique, her piano playing underrated - she was one of my favourite pianists.
Though never signed to Motown, Aretha was considered part of my family.
""Lady Soul" (1968): Another towering achievement, from the accusatory "Chain of Fools" to the sensual "(You Make Me Feel Like) A Natural Woman".
Franklin's career spans six decades.
In 1980 she stole the show in "The Blues Brothers" movie. Her father, the Reverend C.L. Franklin, was a famous preacher whose sermons were played on radio and records.
1987: Aretha Franklin was the first woman to be inducted in the Rock and Roll Hall of Fame. She received our nation's greatest honor in 2005 when she was presented with the Presidential Medal of Freedom.
Earlier this year, music producer Clive Davis revealed that Jennifer Hudson would star in an upcoming biopic about Franklin's life.