My parents are always saying "Oh, you don't like mushrooms, you must have inherited that from your father's second cousin twice removed!" (maybe I'm exagerating... but still!) But I was led to believe that behavior like that was purely how you were brought up and your surroundings.
So my parents told me that they did a test with twins, seperated at birth, to see what they liked/disliked as they grew older. SUPPOSEDLY (since I don't have any sources) the kids liked the same type of toothpaste, the same food, etc. etc. But they were seperated at birth. I don't really believe that, unless I find the research on Google.
So here's the question: Is it genetic, or is it your environment?
edit: Did a Google search, and I discovered that one site says that they will be different, while the other says they are remarkable alike. One says that they most often choose different careers, the other says that they choose the same with "amazing frequency". And so on.