"One of the reasons I wanted to do the programme is I didn't know anything about my grandfather or beyond that because I didn't want to, because he caused a lot of trauma to our family.
"I had shut the door on that."
But it was a journey she finally felt she could take "for my mother because she wanted to know why he was the way he was."
Gibney finds out her great great grandfather James Way Jnr fathered 16 children but he also was involved in an unsavoury chapter of New Zealand history.
He was part of a military invasion of the peaceful Maori settlement of Parihaka in Taranaki in the late 1800s.
She visits the Maori descendants of that invasion and makes an emotional apology on behalf of her family.
"It was incredibly confronting and on the spot I had to come up with a response which was really difficult," she said.
"It had to be treated with incredible care and I was thrown and was terribly emotional.
"The impact on me was quite profound and still has an impact on me."
Gibney also discovers her grandmother was 19-years-old and pregnant when she arrived in New Zealand, from London, in 1913 and then surrendered her daughter, Kathleen, to foster care.
A highlight of her trip was meeting Kathleen's surviving daughter in Auckland.
"It's been a healing time for the family and opened the door on family relationships," she said.
