User blog comment:B214/Volume 23 discussion blog/@comment-172.56.17.58-20170417051436/@comment-31137559-20170419114432

I don't know why Issei and Rias' son wouldn't be allowed to be the heir because there is this to consider:


 * Issei is going to be Rias' proper husband in the future.


 * He is going to inherit the title of Gremory becoming Issei Gremory in the future.


 * He already has the same rank as Rias.


 * He is considered a devil by their society standards and most people have accepted it. It would have been stated if Issei and Rias' child couldn't be an heir to the house.


 * Issei is not a pureblood devil, but he is a devil nonetheless. He is accepted in their society and will kind of be the lord over the Gremory castle.


 * Strength is important in the world of devils. Issei was able to break off Rias' engagement to Riser. Sairaorg was able to take back the position of heir of the House of Bael by defeating his younger brother. And Issei could even become a Satan if he so wishes.

Why would they allow Issei to rise up in rank, be married to Rias Gremory, be considered a devil, and not allow their child to inherit the house? Because his son's blood isn't purely devil. Technically Ex's a half-blood. But in a way could call him a pureblood because both of his parents are devils. Why would they deny someone of Issei's status, fame, and power from having a child that could be the heir of Gremory? The difference between Ex and other halfblood devils is that their parents were actually another species entirely. Issei is a dragon AND a devil. No one is going to deny that. Zeoticus and Venelana would have noted if their child couldn't inherit the house.