But recent research ahead of the centenary commemorations had connected her with a previously unknown cousin, and helped to reunite the family, Ms McLellan said.
"To be able to say to him that you were important to our family, we remember you, and we're part of what you did, is very important to me," she said.
"I feel very honoured to help make him a real person, instead of just a name in a family tree."
The day after Sapper Tobin died, and was laid to rest at Beauval Communal Cemetery in France, Private Piana Pera became the first member of the New Zealand (Maori) Pioneer Battalion to perish on the Western Front.
The 23-year-old Gisborne labourer was travelling through France on a packed train on April 16, 1916, with his company unit when he tragically died.
He was leaning out of a window when his head is believed to have been struck by a trackside object between the stations of Chalons and Chagny.
Pera died from a fractured skull and was buried at Dijon (Les Pejoces) Communal Cemetery. He is remembered on St Mary's Church Memorial Board, Tikitiki, and war memorials at Patutahi and Gisborne.
Today, Sylvia Pene will deliver the Ode in Te Reo Maori at the memorial service to pay her respects to her great grand uncle Piana Pera.
Last year, the New Zealand Army supply technician travelled with the NZDF contingent to France and Belgium to commemorate the Anzac centenary.
While she was unable to visit Pera's resting place, her thoughts "laid heavily" with him throughout the tour.
"On return to New Zealand, I travelled home to Torere, Bay of Plenty, and visited the gravesite of Kararehe Pera, Piana's father, and shared my sorrow of unsuccessfully laying a poppy at Piana's headstone in France," Mrs Pene said.
Today's service, also attended by top military brass and two serving NZDF engineer regiments from Linton Military Camp, begins at 5pm and is open to the public.
