I am confused by one thing. A male Hexenbiest is a Zauberbiest so since baby Kelly is a male shouldn’t it be Zaubergrimm not Hexengrimm??? I’m gonna take a guess here and say the writers forgot that little detail…

It’s a peculiar quirk of the world – when Renard corrects Juliette and says that he’s a Zauberbiest and that’s ‘different’, he sounds like he’s done that a thousand times. Many characters refer to Renard as a Hexenbiest/half-Hexenbiest, and yet they still chose to throw in Renard correcting Juliette and explicitly mentioning that they are different, and that he is unable to open the book. 

From this we’re assuming that Zauberbiests are much rarer than Hexenbiests, are different from them in some major fashion (looks like they have no magic, but that is uncomfirmed) and this is not common knowledge in the Wesen world.

Presumably by making Kelly male, the writers are going to expand on the world of the Zauberbiest, otherwise why have Renard insist upon being called a Zauberbiest and the biological differences between the two?

Here’s hoping, anyway.