Looking for Ratahi of New Zealand

Looking for any relatives of my father Anthony Tani Ratahi. I am the youngest of 9 siblings. Our father was born October 13.1928 in Whakatane,New Zealand. He married our mother; Kura Elizabeth October. She was born July 1.1935 in Te Puke?. Our father passed away May 25.2004. Our mother also passed away Oct. 30.1983.
My grandparents are; Wiremu Mihaka Ratahi & Te Ao Kirimatao Tiki. My great grandparents are; Te Ratahi Parakau & Rooha Petera. I have no information from here on other than the name William Donaldson or McWilliams?. Any information would be greatly appreciated.