Stubborn Leo's?

My 2 yr old son is EXTREEMLY strong willed/ stubborn. If you ask him to do something that he doest want to do he calmly says "no" and then walks away. He doesn't pitch a fit or anything; he just makes it very clear that he isn't going to do what you tell him to do. Some people say that he acts this way because he’s a toddler, but I disagree. He has been this way since birth! Is this behavior characteristic of a Leo?