I'm going to be 25 this year and I still purchase and play just about every Pokemon game, and have several friends around my age who dothe same. Age has nothing to do with anything, let your cousin play the games he wants. Pokemon games are fine for all ages. I like "mature" games as well, even though that's kind of an irrelevant point, it seems important to you, so yes, I have several M-rated games in my collection, and play M-rated titles regularly but that doesn't stop me from enjoying games of other ratings and types. It shouldn't stop you or your cousin, either. There are a lot of great games out there, they don't all have to be gray-tinted first person shooters.