I draw conclusions from your story, your uncle's lifestyle is very bad. because he already has a wife and children, your uncle should be aware that if he does this it will hurt his wife and children. Your uncle still can't control himself that he is old enough and already has a family. It is true that at times like this, financial advice is really needed for your uncle who still likes to spend money, but the first step that needs to be advised to your uncle first is to change this unhealthy lifestyle.
If you tell someone to change their habits which they often do when they are young because they remember that they are no longer young, I think that is a reasonable thing to do. Because most people when they get old really have to change their mindset for the better so that they can teach the generations in their family better, especially if someone currently has children and grandchildren. Of course, considering changing your mindset for the better is the time to do it now without having to wait until you get older.
Because financial advice alone will not have any effect if it is not accompanied by new lifestyle changes from your uncle. With income of that amount, you need to be able to plan your finances in the future so that your uncle can retire early and enjoy the results in his old age with his investments.
In fact, if an uncle's income can be quite large and any money he earns can still be invested by his children and grandchildren, I don't think it's very wrong for him to continue doing so. But he also needs to teach his children and grandchildren to be able to manage existing finances quite well, because money is usually always easier for anyone to spend, but it will not always be easy for anyone to get if they don't have the right method and mindset. So it is very important to teach generations in your own family about things like that for a better life in the future.