This is why gamblers shouldn't hide themselves with the family members if they're gamblers, being honest will make you not face this kind problem in the future.
Alternatively, you could all use the same account, since it's family I don't see why you couldn't trust each other with the amount you play and win, if that is indeed a problem them maybe you need to solve other things first, and worry about gambling further down the road!
This would raise a problem if each of them play using different devices.
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.
Although this problem can be solved if the casino block new authorize while someone already access the account.