Hi Emgee,
Still haven't found anyone with the name spelled Graven but, because they might be useful, if only to demonstrate the extent of the variation in spelling of names in the Holy Trinity registers, I am sending you two lists. The first is of children whose family name begins Gav... and the second is children whose mothers maiden names begin Gav... Unfortunately there are not yet any Grav.. variants even for mother's maiden names, as yet.
[modified: sorry meant to send by PM]
Good luck, and remind me again to repeat the mother's maiden name search when the database is complete.
Sheila