There is a true story?

[Googolplex]

The old Kingdom of Prussia between 17th and 19th century was in northern middle europe. I heared about a Brennenburg Castle in reality. The builder was Alexander of Brennenburg.
And in the castle were some crimes, but nobody really knows about it. There was only one noble man named "Wilhelm" who leave some documents about that crimes.
Where is this castle now?

Is it only a fantasy story for Amnesia, or have it all a true story?

If I google about Alexander of Brennenburg, I can only find it linked to Amnesia.

Here is a text in the remember.pdf from Frictional Games:

Altstadt has never seen much crime, but there was a dark period
spanning from the early winter of 1702 until late summer of 1704.
During these years no less than 39 men were arrested and locked up
in castle Brennenburg’s dungeons. In most cases the criminal’s family
would be banished from the land, effectively cutting the already
dwindling population of Altstadt with 86 souls. The magistrate’s
office has almost no records detailing these crimes, as most arrests
were handled by an unknown nobleman named Wilhelm.

Klaas Gottschall
University of Königsberg


Is it also a real story?