Rahaman Ali, a former boxer, author, and the younger brother of famed American Muslim boxing champion Muhammad Ali, died Saturday in Louisville, Kentucky, the Muhammad Ali Center announced.

According to the center, Rahaman was his older brother’s “biggest supporter,” even writing two books about one of America’s most iconic athletes.

“You can’t tell Muhammad’s story without mentioning Rahaman,” said DeVone Holt, CEO of the Muhammad Ali Center. “He was one of the most constant sources of support during his career, and their relationship was a true example of what it means to be ‘my brother’s keeper.’”

According to The New York Times, Rahaman was responsible for managing Muhammad’s food, scheduling and was always available for him.

Before dedicating himself full-time to supporting his brother, Rahaman was a professional boxer from 1964 to 1972.

Like Muhammad, he changed his name after converting to Islam. Rahaman was born Rudolph Arnett Clay on July 18, 1943. During the 1960s, at the height of the Civil Rights Movement, both brothers joined the Nation of Islam. They later embraced orthodox Sunni Islam in the 1970s.

The circumstances surrounding Rahaman’s death were not disclosed, and funeral arrangements have yet to be announced.