My brother said he doesn't smoke

Maybe he feels like his family is so against it that he would get a lot of criticism if he made it known. Or possibly he doesn't want to worry his family about it. You said he talks about the bad effects of it so at least he knows that it isn't good for him although that is not usually a good enough reason for a smoker to stop. I have a friend that is a "closet smoker" as we call her. And according to her, she keeps it from her husband because she doesn't want to hear the constant nagging about it. I would ask him about it and let hom decide what he wants you to know about it. Happy mylotting!