Rem left the Earth aboard Project Seeds when the planet's resources were all consumed and it became inhospitable. In their search for a new home, the remnants of humanity, with their cryogenically frozen human cargo in tow, traveled the stars and came upon a young Vash and Knives alone on a hostile planet. While most of the crew wanted to exterminate them, Rem stood in the way and saved them. She was treated Vash and Knives like human beings, and not monsters as did most of the crew.
Rem's favorite place aboard Seeds was the holographic Eden that was a smaller simulation of her old home on Earth, without any war, stealing, hate. Vash grew very attached to Rem, and adopted her life philosophy. His brother, Knives, also loved her, but took a different meaning from her teachings, which some see as almost refuting them altogether.