I can't help you with your request for information on the Soehnlein family tree, however my cousin John Soehnlein (Guilford, CT) did some extensive research when he was in Germany a few years back. Our family comes from the Forcheim/Burg area. John was able to trace the family back to the 15th. century in Rottenburg on Tauber. You can find his address under the list of Soehnleins.
Good luck with your search.