User blog comment:B214/Volume 23 discussion blog/@comment-172.56.17.58-20170417051436/@comment-1359322-20170419134235

Why are we still doing this discussion? Also Bennia no, that's wrong. Sometimes i wonder if you read the story or you just spout nonsense without rechecking.

"“Because only the person himself who succeeded the title of Maou can retain the name, this child is a Gremory even though he’s my brother’s son. He’s also next in line for family head after me.”

Heh, so he’s next in line after Buchou. Certainly, he’s the son of the family’s eldest son. Sirzechs-sama may have left the family, but his son is an heir of the important Gremory family."

- Volume 5

Now i'm just going to explain this again as simple as possible just one more time and i expect this issue to end, before i lose control and ban the next person arguing. So here goes

Inheritance line of Gremory,
 * Zeoticus > Sirzechs

But here comes the issue,
 * Sirzechs > Lucifer

Therein lies the problem. There is no heir. Sirzechs doesn't have a son or daughter to fill in his spot he left open. This issue continues till 200+ years later where Rias was born.

Now question time
 * Sirzechs may have left the clan but his right to inherit the clan was still passed down to his children. However he doesn't have a child.
 * Rias on the other hand is already born.
 * So which do you choose in this situation?
 * 1) Rias who is born.
 * 2) Continue waiting for a child which you don't know when will be born?

Answer: Gremory chose 1. So Rias was made heiress. But our little boy Millicas is born about a decade later. So again question time:


 * Rias is already chosen as heiress so she will succeed the clan as planned.
 * But the young Millicas also has the rights to inherit the clan that he took over from his father.
 * How do you solve this?
 * 1) Ignore Millicas and write off his inheritance right like he doesn't own it at all due to a factor he can't control.
 * 2) Return Millicas to his inheritance spot that he took over from his father.

Answer: Gremory went with 2, hence the inheritance right goes back to Millicas, while Rias' inheritance right wasn't passed down.

End of story. Happy, good. Not happy, that's your issue.