Hello
I don't see why it clearly isn't "family council".
When we have something that does not exist in another system, we sometimes just have to translate it word for word as long as it makes some sense in the context, and "family council" does just that.
It is exactly what the writer did in:
https://en.wikipedia.org/wiki/Conseil_de_Famille when he rendered the term in English literally
Also, ruling out "guessing" as you call it does not make much sense where there is no equivalent and clearly right term.
Do you think it is likely that someone is going to propose the right term with 5/5 certainty in this case?
Regards