Well we already know the offspring of Men and Nonmen aren't sterile, since the Anasûrimbor lineage origins from the union of a Nonmen and a human woman. I think the reasons would be more political and religious; since Men try to kill Nonmen on sight, there would be certain difficulties to breed Men and Nonmen. Furthermore, I have the feeling Nonmen consider themselves superior to Men, and perhaps wouldn't consent to such a union. view post