Well, if someone is observant and very much close to each of the family members, there's a high chance that he will notice the sudden changes about the person involved in gambling, especially if that particular person is addicted to gambling already. There will be signs that the person is having difficulties in money or sudden transition in habits and behaviors. Sometimes, those who are addicted develop attitude problem. Temperament becomes an issue, the aggressiveness in making money or begging for money becomes evident.
But if family members tolerate such acts without confronting, there's a low chance addiction will be prevented to further continue and grow. Privacy is essential, but checking the family members, especially if it's children involved, there should be an open communication.
Yes, that's it, I know that privacy must exist even if it's a family, not intending to interfere in the affairs of other family members, I think we also have to take a good approach to find out whether they are in trouble or not.
Obviously temperament will be the most prominent attitude for a gambler, especially if they have lost a lot of money, and it is indeed signs like this that must be watched out for, so that we don't care about the changes experienced by our family members, so we don't regret it later for not caring.