So according to some nutters I am descended from a Guardian of the Holy Grail.
I am descended from a Mennonite bishop, Hermann op den Graeff who was a prosperous cloth merchant. He is one of the signatories of the Dordrecht confession of faith, an important foundation document for Mennonites.
Apparently in his house he had some unusual stained glass windows, that someone decided reveals he was actually the morganatic son of the last Duke of Cleves. What’s more, the windows are said to have secret symbolism showing that the house of Cleves is descended from a Helyas the Swan Knight who allegedly returned the Holy Grail to Jerusalem during the first Crusade.
The talk page on Hermann op den Graeff’s Wikipedia entry is full of exasperated people debunking the crazies.