Hi Ozgirl,
Just a thought:
if you replace "jewish" with "biblical", that could give you
one answer, or rather, one possiblity

There have been many branches of the church (sects, schisms, split-off movements, etc etc -- somebody will probably know a better description

) where the members of the 'new' church gave their offspring biblical names, and once it "runs in the family" then it just keeps going.
It could well be that there is no jewish connection at all
Another theory: originally there was a jewish connection, they converted, for whatever reasons (material gains, less persecution, ... ) but kept their (traditional ?) family names.
Bob