Hi Angela,
The date I found for the marriage between Jantina de Weerd and Willem Hendriks Kuiper came from several web sites which I have listed below:
home.hetnet.nl/~homanfree/kuip.htm (see under VII)
www.geneal.ch/family/parentelen/pvos.htm (see under VI.12)
www.geneal.ch/family/parentelen/phouwink.htm (see under VIII.20)
It sometimes happens that the municipal marriage is on one day and the marriage in church on another but I cannot verify if this is the case here.
With respect to Martha Kuiper and Harm Riks including his parents, you can find more on the following web site:
home.planet.nl/~albert10/Korthuis/BARTELD.HTM (see under VI-j)
In case you need translations from Dutch to English please let me know.
Thank you for your interesting descendence history. There are, however a few names, which are normally spelled differently in German:
Wilhelmie is spelled Wilhelmine
Hinrich is spelled Heinrich
Charlotten is spelled Charlotte
Fredrikke is probably correct when spelled in the Norwegian way, in German it would be Friederike
It would be interesting to know why the family moved to Leer in Germany. There is probably an economic reason as the Oude Pekela region is noted for its poor circumstances especially for those who worked in the peat digging. The shippers were, however, much better off. Leer, as you may know, is just across the border from Nieuwe Schans in Groningen. I passed through there last summer.
I wish you lots of luck with your further investigations an if I find anything I'll pass it on to you.
Best wishes for the holiday season and the new year,
Frans Zonneveld