User blog comment:B214/Question and Answers 6/@comment-199.201.87.147-20180810052638/@comment-10330822-20180813011609

I see it kind of like Lamia or Asari. The Nekomata, if they are all female or not I don't know, reproduce fully with other species to make other full Nekomata. That may be the case even if the Nekomata is "reincarnated" as a devil.

Koneko and Kuroka are examples of that, as Striker said doesn't seem to be any sort of thing as a "hybrid" for the species. A Nekomata's child will always be a Nekomata. It just might pick up additional traits from the other species if there is one. For example, Kuroka and Koneko's children will inherit dragon and probably general devil traits from Issei, just because he is their father.

I wonder personally what the Nekomata birth rate is in comparison to their life span. If its worse than the devils, than becoming a devil may have been a smart choice, because it increases the opportunity Kuroka and Koneko can have children because they have longer life spans.

Besides, devils are stated to have issues making children as well, especially among the purebloods. That's part of the reason there is such a large age difference between Sirzechs and Rias.