Just a thanks to all who contacted me with information.
What I now know is that Edward William Boisen (Ted) was indeed Peter Hansen Boisen's oldest son born in Jan 1885 - his next sibling was Ethel May also born in 1885 (according to NZ B-D-M archives).
The other very helpful information is that this Boisen Family originated from Maugstrup, a small village close to Hadslev.The area was the duchy of Slesvig (Ge: Schlewig) and between 1864 and 1920 the area was controlled by Germany (the Prussinans & Austrians invaded just at the time modern state of Germany was being formed).
In 1920 after referendums in Nth & Sth Schleswig the Norther part was passed back to Denmark & the Southern part stayed with Germany.
In the period of occupation, it seems a lot of Danes emigrated & Peter Hansen Boisen went to NZ in 1874 - it appears an older brother went to the US west coast earlier than this.
In NZ Peter was quickly naturalized and established himself as a noted businessman having part owned a blacksmith business, a stables and also becoming the proprietor of a Hotel in Colyton near Palmerston Nth. Peter was at once time nominated for council and also did jury duty in the area.
Peter had 3 families that are known of :- 1) 5 children from a marriage to Sarah Johnston 2) 1 daughter to one of his employees at the hotel 3) 4 (est) children from 2nd marriage to Ethel Mary Taylor
I am guessing (after doing some digging) that just the #2 branch of the family has 200+ descendants. It seems probable there will be many more via the other branches.
I have managed to gather quite a bit of detail about Peter Hansen Boisen's oldest son Edward William Boisen. I also have several photos of him dating from around 1915 and through to the late 1960s.
If any other Boisen clan member is able to trade pics of other NZ (or even Danish) members of this family please contact me so we can exchange them.