German wikipedia lists 27 Castle Falkensteins. Above is the Falkenstein in the Harz Mountains of Germany. This is said to have been built because of a killing in a duel. Around 1080, Egeno II of Konradsburg slew Count Adalbert of Ballenstedt. To settle the dispute, the killer was made to give his family seat up to become a monastery. (Note that wikipedia calls Egeno a "murderer" but this is wrong -- the killing was public, part of an ongoing feud, so not a "murder" as medieval people understood the word.) As a result, Egeno's son, Burchard von Konradsburg, had the new Falkenstein Castle built starting in 1120.
I could go on, but I think that is enough. So if you need a German noble character for your novel, you can call him the Lord or Count of Falkenstein without anybody being able to tell you that you have his family background all wrong. When challenged, you just say, "No, no, I meant a different Falkenstein family, with a different castle."