Are you assuming your ancestor acted like the "typical Irishman," the "typical German," etc.? Doing so may cause you to believe things about your ancestors that were not true and make brick walls for yourself.
As a simple example, drinking beer is considered by many to be a typical German behavior. Yet in the households of two of my great-grandparents, beer was NOT present and not a part of the daily routine as it might have been in some households. There are a variety of reasons why your ancestor may not follow typical ethnic customs--don't assume behaviors for which you have no evidence.
Most of us don't like it when others stereotype us--let's not stereotype our ancestors either.