Mr Shaw said he decided to come to New Zealand in April and by chance the half marathon was at the same time as his visit.
"I have been told how brilliant the Waipuna Hospice has been to my brother-in-law and sister so I decided to sign up. Deka is more like a brother to me because my sister met him in the 60s when I was a child, he has always been part of the family from my earliest memories."
The past seven years had been torture for the family, he said.
"You feel so helpless, you can't hug someone over the phone which is terrible - you can only listen and be on the end of a phone when needed.
"It really is heartbreaking for everyone concerned and you can't just nip over for a cup of tea.
"That is why I feel the need to fundraise and make sure his sister gets to see him, that is really all I can do."
The 51-year-old will bring Derek's only surviving sister, Sheila, to see him too.
Mr Shaw was born partially sighted due to optic nerve atrophy and nystagmus but it was not discovered until he started primary school.
As he has aged his vision had deteriorated more and now is registered as severely sight impaired or blind. However, he said he has retained reasonable "central vision".
Mr Shaw took up running in his late 40s and he has run two half marathons.
Having completed the Great North Run twice and the Great Scottish Run once, he is hoping to run the Tauranga Half Marathon in less than two hours factoring in jet lag, he said.
Mr Shaw's sister Pam Graham said she had not seen her brother in 10 years.
"I am so looking forward to it. I think he's amazing. Absolutely amazing.
"To take on something like that when he's partially sighted. He's got a really warm heart. I know he's trying to do his best because I've talked about the hospice so many times and they have been a huge help."
The half marathon is on April 12, with the first event kicking off at 7am.
To support Mr Shaw to raise money for Waipuna hospice please head to: www.fundraiseonline.co.nz/michaelshaw/
