Hello/Hallo Egbert,
As a Kretschmann with ancestors from Elbing I - needless to say - more than welcome you to the group :).
I take the opportunity to tell you my story in short:
My great great grandfather Emil Franz Kretschmann was born 1856 in Elbing. Around 1878 he emigrated to the Netherlands.
Emil-Franz had one older brother called Gustav Adolph. But since you say 'your' Kretschmann-line is from Kernei there is probably no direct connection
to my family.
However - in regard to the first name Otto there is one thing I would like to tell you. Have you ever heard of "Otto Kretschmann - Der Zauberer von Elbing"?
See: http://www.elbing.de/982_45-46.pdf. Now this Otto Kretschmann - born 1860 in Mehlsack - is probably not the Otto you mention, but it is a entertaining story.
It would be interesting to see in what degree we are all related.
More info on my family: http://kretschmann.nl
Sincerely,
Milko Kretschmann.
BTW Do you know: ow-preussen-l@genealogy.net? Certainly worthwhile.