I draw your attention to the documentation "Die Villa CAHN in Bonn-Plittersdorf - Ein Deutsches Haus am Rhein" with some personal data, published by the J.P. Bachem Verlag Koeln. A CAHN-family lived in Bonn already before 1772 (banking-house Jonas CAHN founded) unti WWII. Jewish cemetery: "Schwarzrheindorf" 1623-1956 (published by Michael Brocke and Dan Bondy ISBN 3-7927-11990-0 in 1998) and a cemetery "An der Roemerstrasse".
Online you find "Stadt Bonn - Municipal archives" written in English with email-address etc.
