Pretty simple solution, make it so that every family member uses a different casino or bookie, there are hundreds of casinos out there, so there is no need to overcomplicate your life and make everyone in the family play there!
The best to me is to use different sims and devices. They can still use the same site if they have different sims and devices.
At one point you'll encounter KYC, and then the casino will know that there are two members of the same family playing there anymore as you will have the same address, same name, plus, if you use mobile data you might have a surprise of getting the same IP allocated over and over for both accounts as you'll both be in the range of the same cell tower, there is no point in doing it compared o the risks.
Let's say a family of 4 people using the same account, each of them play different games, one playing slots, one playing fantasy sport, one playing live casino, and another one playing dice. The casino might detect the account was used by bots because the account is really active and played by 4 people at the same time.
Personal opinion but in this situation I think the family has a different problem and closing down their account might be for the better!