Five-year-old, Bobbi Gordon, was born with a condition which means she needs medication every day, has to carry an emergency kit for the rest of her life, and getting any illness could mean a trip to the hospital.
But Bobbi's parents, Katie and John, said they were determined not to let the condition define their daughter, and since the start of 2018 the whole family have been fundraising for Climb - the charity which supports them.
Bobbi's mum, Katie, said: "My daughter was in and out of hospital having test after test when she was a baby, it was such a hard time.
"That's why I'm running the marathon, to raise funds and awareness for this charity to help children, like Bobbi, to lead healthier and happier lives.
"The charity supports children and families affected by inherited metabolic conditions.
"There are lots of conditions they support and we need research to find better treatments and help give them a better quality of life."
She added: "We were determined not to let this condition define her, and not to wrap her in cotton wool. Five years on she is a crazy kamikaze little lady, just like her mummy!"
Last year, Katie decided to do a ‘4 before 40’ challenge to support the charity - "Four sponsored running events before I hit the big 4-0", she explained.
Katie's first official challenge was the Bolton Abbey Festival half marathon in February, but along the way family and friends have got involved by doing other sponsored runs, sponsored climbs and even a sponsored head shave.
The family decided to brand themselves as a team, and consulted 'horse-obsessed' Bobbi, who said they should be called 'Team Hercules'.
Katie explained: "The main reason is due to Bobbi’s (sometimes unhealthy) obsession with horses.
"She has hundreds of toy horses - plastic horses, stuffed horses, horse t-shirts, horse leggings. To be honest she thinks she is a horse half the time, she whinnies, she neighs, she trots and she gallops.
"Last year we took her horse riding for the first time and she fell in love with her horse, a small brown and white pony called Hercules."
After four months of various fundraising efforts, Team Hercules have raised more than £3,500 for Climb, and Katie hopes to get even more donations after this weekend.
On Sunday (April 22) Katie will complete her fourth and final fundraising challenge - the London Marathon - with her sister Jane, who will even be dressed as a horse!