Aretha Franklin may have spent decades hiding one of the biggest secrets of her legendary life.

The Queen of Soul allegedly carried on a secret, on-and-off romance with James Brown for roughly 40 years — and only opened up about the relationship near the end of her life, according to a source.

Franklin died in August 2018 at age 76 after battling advanced pancreatic cancer. Now, as the eighth anniversary of her death approaches, claims about her private relationship with the “Godfather of Soul” are once again raising eyebrows.

“She kept it to herself all her life, but Aretha’s heart belonged to James,” the source claimed.

The insider added that Franklin and Brown shared a deep connection that outsiders may never have fully understood.

“Aretha and James had a lot in common, more than most would think,” the source said.

The alleged romance would have unfolded largely behind closed doors while both music legends were involved in other relationships.

Franklin was married twice. She wed Ted White in 1961, but the marriage ended in divorce in 1969. She later married actor Glynn Turman in 1978 before the couple split in 1984.

Brown also had a complicated love life.

He married Velma Warren in 1953 before they divorced 16 years later. He later wed Deidre Jenkins in 1970, with that marriage ending in 1981. Brown married Adrienne Rodriguez in 1984, and the couple remained together until 1996.

Despite the alleged decades-long affair, Franklin and Brown never publicly confirmed they were romantically involved.

They did, however, cross paths professionally.

In 1989, the two powerhouse performers joined forces for the duet “Gimme Your Love,” giving fans a rare collaboration between two of the most recognizable voices in American music.

Brown died on Christmas Day in 2006 at age 73.

Franklin continued performing for years afterward, cementing her place as one of the most celebrated singers of all time. The “Respect” icon won 18 Grammy Awards during her extraordinary career.

Her death on August 16, 2018, triggered an enormous outpouring of grief from fans, entertainers and political leaders around the world.

“We have been deeply touched by the incredible outpouring of love and support we have received from close friends, supporters and fans all around the world,” Franklin’s family said following her death.

Franklin was laid to rest after a star-studded funeral in Detroit on August 31, 2018.

The lengthy service drew some of the biggest names in entertainment and politics, including Smokey Robinson and former President Bill Clinton.

Robinson, who had known Franklin since childhood, delivered an emotional farewell to his longtime friend.

“We talked about it many times, how we were the two who were left out of all our neighborhood friends,” he said. “We were the longest ones. Now my longest friend has gone home.”

He also recalled one of their final conversations, saying Franklin had spoken about plans for a movie about her life.

“I’m gonna miss our talks,” Robinson said, later adding that Franklin would surely have “one of the featured voices in the Choir of Angels.”

Clinton also paid tribute to the singer, praising Franklin for the strength she displayed throughout her life.

“This woman got us all in the seats today not because of her music, but because she lived with courage,” he said.

“She lived with faith — not without failure, but overcoming her failures. She lived with power — not without weakness, but overcoming her weaknesses. I just love her.”

Whether Franklin truly carried on a decades-long romance with Brown has never been publicly confirmed by either star.

But if the source’s claim is true, one of music’s most legendary voices may have taken an extraordinary love story with her to the grave.