User blog comment:B214/High School DxD EX/@comment-213.120.234.106-20151104110036

Here's a question. Out of all of Issei's kids in DxD, why is it only his kid with Asia who has his surname? I understand Ixis, because he is the son of a high class devil and royalty keep their name seven if they marry. What about the others though? Like Kurenai and Zen? How come they don't take their father's last name?