My little sister has Cystic Fibrosis. She's 16 but is very frail for her age and has had many lung infections and stays in the hospital. Our father recently started smoking and he's been doing it in the house a lot (he's been depressed lately for various reasons). Because of it my sister has been coughing a lot more and its having a bad affect on her already low functioning fragile lungs. When my mother and I talk to him about it he doesn't listen, at least he hasn't yet. What should I do and how can we get him to stop? I'm very close to my sister and I don't like to see this.