Aw, I can't take the credit for that - I found the (grand)father's wiki page first, took an educated guess which of the three sons might be the one in question, and when I googled his full name, Fontane was basically the first thing that came up. But it was a nice reminder indeed that he put some research in when it comes to Brandenburg and its history.

Love your take-away from the Lehndorff quotes, hee.