Floyd Mayweather's uncle Roger, who also trained the boxing legend, has died.
The 58-year-old, who was also a professional boxer until 1999, is believed to have been suffering from poor health, including diabetes.
Roger trained his nephew when he turned professional in 1996 until his father was released in prison two years later.
He returned to Floyd's corner between 2000 and 2012 as he became recognised as the best pound-for-pound fighter in boxing.
He later developed memory problems and went missing for several days in Las Vegas in 2016.
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"My uncle was one of the most important people in my life inside and outside of the ring," said Mayweather.
"Roger was a great champion and one of the best trainers in boxing.
"Unfortunately, his health was failing him for several years and now he can finally rest in peace.
"Roger meant the world to me, my father Floyd Sr., my uncle Jeff, our whole family, everyone in and around the Mayweather Boxing Gym and the entire boxing world. It is a terrible loss for all of us."
Mayweather Sr won 59 of his 72 professional fights and held the WBA and lineal super-featherweight titles from 1983 to 1984, and the WBC light welterweight title from 1987 to 1989.
He was nicknamed the Black Mamba which he attributed to the snake of the same name.
"It’s funny because I wanted a boxing nickname that wouldn’t be common to most people," he said.
"One day when I was flipping through channels and I came upon this channel showing different reptiles, and they were showing the black mamba, one of the deadliest snakes in the world.
"I loved the way the mamba attacked so quietly, but when he hit you he just hit you one time and the poison was in you.
"That reminded me of myself right there."
Mayweather Sr was rarely far from controversy even after he hung up his gloves.
He was fined $200,000 and banned for a year in 2006 for brawling with Zab Judah's trainer and father Yoel after Mayweather Jr's controversial win.
And he was arrested in 2009 in Las Vegas for allegedly attacking one of his former boxers, Melissa St. Vil.
Mayweather Sr pleaded no contest to two charges and was fined and ordered to carry out community service.
His uncle's death comes a week after Mayweather Jr's ex-girlfriend Josie Harris was found dead in her car outside her home in California.