User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-173.71.153.83-20150210171741/@comment-16281343-20150226093246

No. Everyone down Rias and Issei's lineage will not be considered as a pure-blood.

If it weren't for the existence of Millicas, Rias' relationship will not work as smooth like it is as they want to preserve the House of Gremory and prevent it from becoming an extinct house.