A trailer's job is to sell te product. One of the staples of F4 is the family dynamic. It's not unrealistic to expect that to be shown.
The trailer is selling the movie. You know who it's not selling the movie to? The tiny percentage of it's potential audience that actually reads Fantastic Four comics. Like all big budget comic book movies, it's selling to a mainstream audience. Of course the family dynamic is important, but I'm not going to act like Trank completely ignores it based on a two minute trailer.