Firstly, confiscation of funds is illegal (unless it is bonus money from the casino). Secondly, I think this issue is resolved through the support service. And it seems to me that the casino itself initiates the solution of this issue through a request of KYC procedure. One IP address for an entire location is a known problem and casinos do not want to reduce the number of their clients because of this. I think this issue is easily resolved (especially if you are not a bonus hunter or something like that).
I doubt that the casinos will taking serious to accounts that aren't earn, instead they will act like nothing happen because the more people loss, the more they earn. Based on my experience when all people of the family installed or use the same thing, it's always related to taking advantage over something.
In this case they might take advantage over bonus, even each of them can submit their own KYC, but technically they still broke the one IP address rule.