My boyfriend smokes..should I break up with him?

So I started to date this guy and I believe he was mister perfect until today when I saw him smoking while walking home. I thought he was the best guy in the world, which he is! He loves everything I do and he's really sweet, but I'm afraid. My grandfather died from lung cancer and heart disease and my grandmother had smoked but she quit after her husband died. My parents are really strict about smoking and so am I, so should I break up with him for it? My dad told me it took his father to die for his mom to stop, so I shouldn't even try. What should I do?