Bemerkung: When I received the information from DW Jakob was documented as being the son of Johann Wilhelm and Friederike (nee Loos) GUCKERT.
Subsequent research at the Evangelical church in Guntersblum showed that there were three sons in Johann Wilhelm's generation; and one other also had a Jakob, which then raised the question of which was the one who emigrated.
Upon revision of the documents back in NZ, the marriage certificate provided the break-through clue, and states Jakob's parents were Peter and Dora, or as they officially are Johann Peter and Ann Dorothea (nee Schallus) GUCKERT.
As I deem that Jakob was fully aware of who his parents were when we got married I am assigning the Jakob who emigrated from DE to NZ to the later parents.
The family tree from AG in Guntersblum, Germany also concurs with this.