In this movie the producer not only just kills off the mother but they also kill off the father as well. I believe they do this because there would be no movie if the parents existed for the entire time. Just like Finding Nemo, there would be no point if the mother was still in the movie. With the parents being gone I feel like that is what made Anna set out to go find her sister Elsa. If her parents were there her powers would have been in control and none of the big ice storm would have even happened. Therefore without that there is no plot. With that being said clearly the producers did that on purpose. They didn't try and be unfair, like as stated before. Once again I just think Boxer is getting a misunderstanding on what Disney and Pixar
