Harry Byrne may only be six, but he's already taken on a monumental challenge, all in the name of his baby brother Rueben.
For his parents Sophie and Sean, it's not the first time they've had to watch a child go through this. The pair lost their daughter Olivia to the same condition eight years ago and say it affects just 17 people worldwide - including their children.
Harry, who has watched local childrens hospices in Wiltshire in the UK care for Reuben, decided he wanted to give back and set about planning a sponsored walk.
While the original plan was the walk the 72km (45 miles) between the hospices - Julia's House, Naomi's House and Jack's Place, lockdown restrictions meant he couldn't take that route.
Instead, he devised a new plan, walking 24km each day for three days, joined by dad Sean, to raise the funds.
Not even the freezing conditions or snow could put him off.
"Harry has experienced first-hand how these wonderful charities help and care for his brother, Reuben and support us as a family," Sophie wrote on a fundraising page for the event.
"Harry expressed his desire to thank the wonderful charities of Julia's House and, Naomi's House and Jack's Place. To raise awareness and vital funds, he will embark upon a sponsored walk. The walk will cover the distance between the two hospices (45 miles)."
While their original target was $2700, they've since raised more than $21,900 for the charities.
After training up for the journey, Harry and Sean set off, completing each daily target, as Sophie and Reuben cheered them on, joining in where they could and Sophie posting updates to Facebook.
"Final day of the challenge! We've had snow. Harry really wanted to take Reuben out, to make some special snow memories. Reuben enjoyed joining him for two miles," Sophie shared.
After completing the challenge, Harry celebrated by making a snowman, saying: "Thank you so much for your donations, it will make a big difference for the charities, guys you are amazing!"
As Sophie told local news ITV News, he had been a huge help with his brother, even fetching the oxygen tank when he has a seizure. Harry was determined to undertake the adventure, and they were extremely proud.
"Sean and I were so touched that he wanted to do something for his brother, so he can reflect on the positivity and give back to the charities that help us, there was no way we were going to stop him," she said.