"Members of the Maori Women's Welfare League would talk to young women like my grandmother, essentially saying such relationships were not a good idea," Hansen says.
Her grandparents had 13 children but did not marry until 1981, waiting until her grandfather's wife, whom they all knew about, died in China.
His two Chinese daughters eventually came to New Zealand and were welcomed into his family here.
Hansen has used the relationship as a basis for her debut - and award-winning - play The Mooncake and the Kumara.
"In the play it's love," she says, "but in reality they had a life of respect, gratitude and kindness together. They really cared for one another."
As well as having her play in the Tauranga Arts Festival, Hansen is also speaking about her work, which includes scripting a possible television series about the "apartheid" of 1960s Pukekohe.
She will be joined at the festival by historical novelist and Tauranga resident Debra Daley, who has also written for television, including episodes of 1980s soap Gloss. For her most recent novel, Turning the Stones, and her forthcoming book, The Revelations of Carey Ravine, Daley immerses readers in the 18th century, a period she adores.
"There was a passion for literature, the development of the novel and new modes of personal expression that are the beginnings of romanticism. I always loved 18th-century literary style - its wit, irony and nuanced writing," she says.
"Women began to be published more widely and to find ways of earning a living as authors, translators, editors and typesetters. The 18th century sowed the seeds of the hyper-capitalist age that we live in now and it fascinates me to note the parallels with our own age."
Both women enjoy immersing themselves in research with Daley spending a lot of time in the British Library in London.
"It is a repository of original 18th-century English texts, letters, journals, diaries, newspapers, pamphlets. That kind of 'from the horse's mouth' research is great for recreating 18th-century dialogue, and finding the correct nomenclature," she says.
"My aim is to give the reader a 'time-travel' experience - to make them feel as much as possible that they are in the 18th century. If it is a particular landscape I want to describe then I will go to that place if at all possible and take photographs and draw maps."
A professional writer and editor as well as a novelist, Daley attends a weekly yoga class at Mount Maunganui and tries to fit in a couple of treadmill sessions at the gym "just so I don't lose the use of my legs completely from so much sitting".
