Just had a quick read through this thread.

Is my understanding correct, only the parent who is earning in the family needs the language requirements?

Reason I ask is that my wife and I both recently did the B2 exam. We don't have the results yet but I am reasonably confident I passed. My wife not so.

Therefore, our current thinking is that me and the kids can get our C permit and my wife will have to wait until she has her language cert...