Hello Shirley and Roger,
I would like to support Roger's opinion:
Having done extensive research yet mostly in Northern Germany, I haven't come across one interreligious marriage before about 1880. There have been conversions to mostly Lutheran or seldom Catholic faith before: - in Breslau/Wroclaw I saw quite a few civil marriages in that time where the names of bride and groom and family members gave hints for a possible conversion.
The tolerance of Mennonites towards Jewish faith may resolve them also being in the focus of prosecution. Where Jews were allowed to settle, the authorities may have been tolerant enough to have other religious minorities staying there, too (example Friedrichstadt in Nordfriesland). But this is just my guess.
I have just checked an interesting German database on the distribution of names in Germany. I entered Wilbers which isn't really common and doesn't at all sound Jewish to me.
And here's the link to a database of Jewish families in Krefeld - no Wilbers, also no W. in the Memor-book.
The only way to solve the question is by doing further research going back step by step, keeping the question in mind.
Good luck and kind regards from Germany
Corinna, near Hamburg, Germany