Jonjo Heuerman, 11, is walking across two counties, clocking up almost 30 miles.
He took on the task in memory of relatives from NI which he lost to cancer.
He began his three-day trek for Cancer Research on Thursday at his great-grandfather's final resting place of Laurencetown in rural Co Down and will end it at Milltown Cemetry in busy west Belfast where his great-grandmother was laid to rest.
Jonjo said that he began organising walks after his granny died of the disease. His sister raised over £10k for their local hospice and he decided he wanted a challenge too.
Since then, he has organised events and awareness appearances including a '66 miles in six days' walk, and also 23 and 27 mile walks.
It is estimated that over £1m has been raised in awareness for Cancer Research UK through his public appearances. Young Jonjo has also gathered over £100k in public donations.
My ultimate goal is to keep on raising money until cancer doesn't exist.
"I'm very happy because loads of people have been helping me and loads of donations have been made," he said.
On his latest walk, he added: "It's a really special walk because both my mum's grandparents died of the same disease in Ireland."
Jonjo hopes people will come out and show their support for him along his route.
On Saturday, the final day, he will carry a floral tribute for all of the people listed on the special t-shirt he is wearing on the walk and at the end, he will call out all of the names when he lays the flowers at his grandmother's graveside.
His mum Donna left Belfast with her family in 1970 when the Troubles broke out, but has a huge family circle in the region.
Of her son's non-stop fundraising, she said: "He does wear you out a little bit and it is hard to keep up with him.
"But I think children should be encouraged, not discouraged. It is good to do good."