The project, which is about a married couple dealing with the emotional fallout of a traumatic event, was conceived of and shot as two companion movies: Him and Her, which shared scenes, but made up of different takes, performances and direction, to reflect the experience of either partner. One or both of the Weinsteins decided, however, that no one would actually buy tickets to both movies, so they ordered a theatrical release that mixes in parts of both. As I understand it, therefore, Him and Her do not duplicate any of each others' actual takes, but there is nothing in the (barely) released film, Them, that is not in either part of the companion movies.
The development and re-editing story is kinda interesting, but I can't say as I'm much interested in actually watching any of the three films.