Fantasy; original, crossover, or timetravel.  For whatever reason, a kid who's had a very good and thorough education in the use of his/her powers (they've had them since birth, and since their parents were involved in the supernatural they had the benefit of learning how to use them along with everything else like walking and talking; by this point, they use their powers very fluidly and naturally) and an adult/older teen who's new to their powers, clumsy with them and possibly afraid, have to live/travel together.  Post-apocalypse, maybe?  Not many other ways to fling together an adult and child who don't know each other previously.  The adult has to do all the adulty things--protecting the kid, making sure they have enough food, etc.; but the kid has to teach him what he needs to know, because the situation's dangerous enough that they need to use their powers to stay safe.