~snip~
Ok but even then if a gambler is very good at hiding it, it's difficult for a family to find out about it. Drugs and alcohol is so much easier because when you are wasted, you are wasted. No questions need be asked whether you have a problem when you are wasted five times a week.
But gambling is a different issue. Unless someone crosses the line and starts stealing money or borrowing money in excess of what has ever been usual in the past, it is still complicated to find out about it unless the person himself approaches their family and tells the truth. To get back on topic here, financial dependence can also mean several thing. Even if someone earns tons of money but has a costly lifestyle based on long-term obligations, financial dependence is still a thing. If there are existential dependencies and money is at risk that would have to be used otherwise, the problem can quickly overwhelm even someone who seems to be financially independent to outsiders.
Not necessarily because the relationship between the members is close, they will know if there is something different with the other family members and will ask them directly. And it doesn't take long for those family members to know there's a problem or that all is well.
If someone has a lot of money but has an expensive lifestyle, it will depend on how much money they have but the money will surely run out if it is not managed properly. Especially if they use their money to gamble and don't limit it properly.
And back to the topic. It seems that it is necessary to discuss this gambling problem with his nephew so that he understands that having a gambling habit is not good and will even have a bad effect on that person. Hopefully, his nephew can understand the conversation and won't come close to gambling again, even though he's an adult. But it also depends on how he wants to avoid gambling.