While the later films in the Potter series drew in a solid fanbase throughout the 18-35 demographic, Fantastic Beasts is so far on track to be an older fan event.
The fact that Fantastic Beasts is appealing primarily to adults right now shouldn’t really come as a surprise.
Putting aside the question of whether or not the Fantastic Beasts franchise could ever even come close to the success of Harry Potter, it’s worth noting the shifts the franchise saw in its demographic over time.
By the time Fantastic Beasts 2 comes around in 2018, that “over 35″ demographic just might be bringing their children along, thereby building up a future audience of proverbial “Potter nerds”.