Board Thread:Questions and Answers/@comment-79.27.35.119-20190410172623/@comment-6697950-20190917191325

The anime kinda glossed over the actual explanation. They copied the Fluctlights of exactly 12 babies, got rid of any variance between them to create a blank slate template, and then just copied that template every time they needed a new baby in Underworld (automated by the system when certain requirements are met). So, no one in Underworld actually has an equivalent person in the real world.