Hello Bob, is this your family I have just found them on the online IGI this all needs to be checked,

Robert Christian and Sarah Ann Dennis
married, 5 June 1875 Lyttelton

Baptism,
Robert George Christian
born, 1886 Lyttelton
death, 1950
Father, Robert Christian
Mother, Sarah Ann Dennis

if you don't have the Birth Cert. of Robert George Christian, it is a good one to get,

get the electronic copy (available to purchase online) from NZ BDMs
it has a lot more information on it, you get place names as well as Country,

was Robert's marriage to Margaret Boyd, the second marriage ?

Averil