The uncle JACOB LEWIN Christening: 17 FEB 1850 Saint Lukes, Baldwin, Isle Of Man, Father: CHARLES LEWIN, Mother: ISABELLA CAINE [IGI].

If the right family for your William (and do please first order photocopies [not certified transcripts] of those NZ certs if you don't already have them), he might have gone to NZ with his brother James. The certs should also have how long in NZ, so that you can check passenger indexes.

Sue