Supernatural... Let us break it up.. Super.. Natural Defined.. Something that is above nature.. above the scope of the nature of the world. Natural Laws, the laws by wich the world is run. Therefore the only thing that are supernatural are the things taht are created by the mind. If something exists in this world then it in following the nature of the world, and so must be natural.
age is indeed just a number. maturity and experience should be a more turned to indicator of a person's ability to deal with situations and events. There are people who are over the age of a leagal adult but have to mentality and/or personality of someone younger, and vise versa.