Nexes - The Steel Heart

Name: Nexes
Gender: Female
Element: Metal
Background:
It started soonafter the original six nobodies were created. Xehanort, now Xemnas, realized that his feelings for Braig, now Xigbar, were dangerous. He used a machine to get rid of them, in a way similar to how heartless steal hearts. The disconected emotions took the form of half a heart, and were tossed into the darkness. But the darkness bonded with the half-heart. The heartlet, as it was later named, basically bonded the darkness together to create a human shape. It was a nobody, made from darkness with the body of a 17-year-old girl. It crawled out of the darkness and Xigbar convinced Xemnas to let her live, teaching her how to be human(or whatever) and naming her Nexes. Nexes was a fast learner, and soon rivalled Xemnas in scientific expertice.

Using what they learned from her, they made the Darkheart, basically a heart made from darkness using small bits of a real heart to hold it together. There were several mistakes, including Plauge, a nobody whose body began to rot away shortly after creation, and Nemo, a mentally retarded nobody created without eyes. Saix was another mistake, created with limited feelings. He was created as a replica of someone from Xemnas' past, so they kept him. Axel was the first sucess they had with the Darkheart, because he had simulated emotions.

And that's why they have emotions, despite being having no hearts.