Rem was a member of Project SEEDS, a project dedicated to moving Man Kind from Earth to a new planet. During the process of moving mankind to the new planet two children were born, it became Rem's responsibility to take care of them. She is a very kind woman who would never hurt a thing. The two children were Vash and Knives, she taught them to never hurt anything and that all life was precious. As well as a caretaker of the boys she was a strong member of the project SEEDS crew. Everyone listened to what she had to say and they all respected her.
We do not see the crews deaths, but Rem, Knives and Vash are running from the doomed spaceshipe to an escape pod. However Rem opts to save humanity before herself. Vash often remembers Rem and she is practically the only inspiration he has to go on in his life at first.