Mr Wilkins' grandfather never fully recovered from the combined effects of being gassed and the appalling conditions of trench warfare, dying at the comparatively young age of 68 while he was still a small boy.
"My grandfather was not a well man."
But the stories passed down from his grandfather Marcus to his father Marcus and now to him had become an important part of the Wilkins family narrative.
The descendants and extended family of the soldier who celebrated his 21st birthday in the trenches would also be placing crosses on memorials to three soldiers cut down in the prime of their lives.
They were an uncle of Mr Wilkins' mother Jan, the great-uncle of his wife Nicola and the great-uncle of his brother's wife. Two were killed in the earlier stages of the battle that ran from July to November 1917.
"Three died and one got home," Mr Wilkins said.
How his grandfather survived the horrors of The Somme and Passchendaele had been passed down father to son, with the normal generation gap changed because the returned soldier did not father a son until he was 39 years old.
"That is why it is three generations removed rather than four."
His son Marcus George, called George to avoid confusion, will join his parents and grandfather on the trip to the commemorations.
Mr Wilkins said everything he knew of the battle was what his father had told him or what he had heard and read. On Thursday this week, he attended a discussion at Tauranga Boys' College on Passchendaele, entitled "New Zealand's Darkest Hour."
This was because the failed attack on Bellevue Spur on October 12 left 845 New Zealand soldiers lying dead or mortally wounded between the lines. A further 1855 soldiers were wounded, making it the darkest day in the country's post-1840 military history.
Mr Wilkins said his grandfather opened up about his wartime experiences later in life, with stories still being told on the veranda of the family's Pongakawa farm into the early 1960s.
He said his father was a young man helping out on the farm after World War II when Marcus the returned soldier began talking about his experiences in World War I.
Mr Wilkins suspected his grandfather would have opened up on the occasions when his father used to drive him home from the RSA.
Planned highlights of October 12 Passchendaele commemorations
11am: Join commemorate service at Tyne Cot
3pm: New Zealand Memorial Poppy Garden opening
4.30pm: Special tree planting
7.15pm: New Zealand sunset ceremony at Buttes Cemetery