Hi Dinah
Welcome to RootsChat.

And you are doing just fine with the presentation of all this information.

Yes, it does appear perhaps that Isaac CHERRINGTON did not marry ... can find no entry on the NZ Marriage Index.
And I guess that as you have cemetery information for him, that search might also have revealed any other CHERRINGTON"S buried nearby ?
[BUT ... depending on when in the 1870's the family came back to NZ, Isaac could have been of an age, to have married whilst still in Australia, and returned to NZ with a "bride" ? It may be worth posting a look-up on the Australian board to check if there was a marriage there for him ? ]
Lu