User blog comment:B214/The one-shot answer ranting/@comment-77.188.219.183-20170424164001/@comment-26709288-20170608120845

keyword: died without children.

Sirzechs didn't die without a child, he just didn't become heir. This is the problem with trying to use real life with fantasy/mythology. Devils live for 1000s of years compared to humans 100. Sirzechs and his father are still alive, there wasn't a need for a heir. Also pay attention to the gap between Rias and Sirzechs compared to the gap between Rias and Millicas. That's the problem