Just spent a solid half hour reading the wikipedia pages for all the brat pack films.
I think anything that is EVEN REMOTELY related to any member of the brat pack should be considered a brat pack film. For example: the TV mini series "The Stand" based on the Stephen King book is a brat pack film. The TV show "Parks and Recreation" is a brat pack film. The first 15 minutes of the first Mission Impossible movie is a brat pack film.