User blog comment:B214/Season 3 confirmed!!!!!!/@comment-24.104.16.162-20150329163637/@comment-1359322-20150401235950

"Buchou also spoke while giving an amused smile.

“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."