Most gamblers hide their gambling is because they feel ashamed or afraid of being criticized by their family. So if you are thinking of telling your friend's addiction to his family, try to consider his or your relationship with his family. See if telling his family would have a good impact on his gambling addiction. Family can help better with addiction, they can support their loved ones well. And if not, then it's better to support your friend and push or recommend him to seek professional help.