Hi Bob,
I still think that the possible family I found for him in Kk German, described in my message of 9 Feb. is the best bet:
http://www.isle-of-man.com/cgi-bin/interests/genealogy/bulletin/index.pl?noframes;read=521249
My suggestion after that for what you can do in NZ is to order photocopies (printouts) from the Office of Births Deaths & Marriages of the birth entries for ALL his children. I know this is pricey, and if too expensive you could try them one at a time until you get lucky.
I explained that I got ones for seven children during the 1870s and 1880s for my family where their mother was from the IoM, and four of them gave the correct parish for her. The others just had IoM. She was the person who had registered most of their births.
Hopefully your Robert Christian will have registered some of the births himself, and put in his correct birthplace.
It is important to order printouts, not a birth cert., because not only are printouts cheaper (because not certified), but sometimes the transcripts miss out information. The printout, being an uncertified photocopy of the entry, has the complete information.
Office of Births Deaths & Marriages, PO Box 10-526, Wellington 6143. Email: bdm.nz@dia.govt.nz
Good luck.
Sue