Is it normal that i became a smoker will still underage

I am the only child of two smoking parents and smoked my first cigarette at 15. At first not too often but before I knew it was smoking daily. When I told my parents I smoked at 17 I already smoked close to a pack a day. My dad told me they already had figured out I had started and were not too surprised I was a smoker now.
Is it normal to pick up smoking at that age?