gambitten's state archive link says he was called Hans Heinrich von der Gröben, so not the wiki guy it seems.
By the way, two of those letters are actually at Trier, and while, sadly, not the ones with anatomical details, the second one has Fritz writing verses in German for him (!) and the poem seems to have three lines either censored or corrupted, so you are free to speculate what was in those lines :P
Very rough translation, because I'm not sure I entirely understood everything:
"Gentleman [cavalier] full of whims and other antics even though I haven't gotten any written message from your dear hands in a long time telling me how you are and if confusion keeps triumphing with you (??) ... ... ... The noble red wine stings my brain today, so that I even forget the course of the stars, so closes the poet, wishes you to live well, and gives you good night a thousand times."
Re: New and Upcoming Sources Pt. 1
By the way, two of those letters are actually at Trier, and while, sadly, not the ones with anatomical details, the second one has Fritz writing verses in German for him (!) and the poem seems to have three lines either censored or corrupted, so you are free to speculate what was in those lines :P
Very rough translation, because I'm not sure I entirely understood everything:
"Gentleman [cavalier] full of whims and other antics
even though I haven't gotten any written message
from your dear hands in a long time
telling me how you are and if
confusion keeps triumphing with you (??)
...
...
...
The noble red wine stings my brain today,
so that I even forget the course of the stars,
so closes the poet, wishes you to live well,
and gives you good night a thousand times."