Sources of the Staufen family : what can it be said ?

Question:

Sources of the Staufen family : what can it be said ?

I have found no historic details of the origin of Fredric of Beuren, founder of the Hohenstaufen House .
I was taught he was unknown before his marriage with Agnes, daughter of Holy German Emperor Henri V........but for the present european monarchs, more is available even if documents do not exist !

Best Answer - Chosen by Asker: http://www.genealogie-mittelalter.de/sta...

http://www.mittelalter-genealogie.de/mit...

Both of the above are in German - however, they contain info. & sources for both Frederick I of Swabia, and his father, Frederick von B㼲en.

Hope it helps.