User blog comment:B214/Volume 23 discussion blog/@comment-31764731-20170419212923/@comment-31137559-20170420154949

That's because they were another species that were turned into devils. While their children will be born human or whatever other species, they will probably also be become devils because their parents are reincarnated devils. Issei's and Irina's son, Shin, had one angel wing yet Irina is a reincarnated angel. Reincarnated only applies to those that weren't originally devils. Now Issei's children will be dragons, but they will also be devils as well. If Saji had a child, most people will probably imagine his child will have the aura of a dragon despite Saji not being a dragon himself. I really don't think it would be all that different for the children of reincarnated devils.