Mr Motivator has announced his 12-year-old granddaughter Hadassah has died after a five-day battle against meningitis.
The health and wellbeing coach, real name Derrick Evans, said she died in the early hours of Thursday in Antigua, where she lived with her mother.
Their relationship was described as "incredibly close" by a source close to the family.
Hadassah’s mother, Caroline Evans Charles, is Mr Evans’ eldest daughter.
In a statement Mr Evans, who is from Leicester, said: "It’s not meant to happen like this. The circle of life dictates that parents and grandparents go first.
"You are not supposed to bury your child or your grandchild."
Mr Evans said: "We have to fight on no matter what.
"I want to remind everyone to tell your loved ones every day how much you love them."
It has been reported Mr Evans’ wife Sandra has flown to Antigua to be with the family and he will join her as soon as possible.
The TV fitness instructor found fame in the early 90s and is well known for his neon lycra and upbeat style.
He was awarded an MBE in October 2020 as part of the Queen’s postponed birthday honours list, for services to health and fitness after creating online home exercises during the coronavirus lockdown.