Considering the previous movie "Goodnight, mommy"...
Considering that it was the same director of "Goodnight, mommy", of course the kids were the bad ones. When the stepmom heard the girl talking to the phone and demand some answers and she went like: "I was just pretending", I knew something fishy about those kids
And considering the previous movie "Goodnight, mommy" I was specting a good movie, not this trash