There are many many Ubbens located in the Ostfriesland area of Germany. When I visisted there several years ago there were over 300 listed in the phone book for the Ostfriesland area of Germany alone. It is unknown how many are in the rest of Germany.
The Ubben Tree which I have posted on my website is only a small portion of what I have in my Family Tree Maker program. I have been working on my father's ancestry for approximately 25 years. The sources of my information are many, but the Ostfriesland Genealogical Society of America is probably the most significant. Through them you can buy the Ortsippenbüchers, (Area-Family-Church-Books) for the Ostfriesland area.
If I can help you, don't hesitate to contact me further. You may E-mail me at Duzbruder@access-one.com