Drost Isselburg en Hetter, vader op verschillende plekken anders.

https://books.google.nl/books?id=_oYAAAAAcAAJ&lpg=PA728&ots=xgjrET2SiF&dq=%22casper%20von%20syberg%22&hl=nl&pg=PA700#v=onepage&q=horst&f=false

https://www.genealogieonline.nl/genealogie-richard-remme/I31297.php