Lost family from Norsewood New Zealand

I am looking for desendants from Oline and Fredrick mortensen who came to Norsewood on the Holvdig (not sure of spelling) in 1872 from Norway. They settled in Norsewood and were one of the first settlers there. I think they had many children who came out with them. i am a desendant of one of their sons who i am sure was the oldest Fritjof Mortensen. He left his family (children and wife) and ranaway to Australia where he changed his name to Morton to hide the fact that he had commited Adultry. i believe he died in Australia in about1930 something i am not sure. I am searching for all living desendants from him (his family he left behind in new zealand) and any other infromation about his ancestors and parents would be much apreachiated.