User blog comment:B214/Volume 22 spoilers/@comment-95.90.227.74-20161018202609/@comment-1359322-20161019003453

@Main comment. Benefactor yes. Parents no. They only provided a body to an existing person/being. They didn't really create or give birth to Issei.

If simply providing a body or having DNA makes them blood-related, then the Plate Mail army Qlippoth use would be all be considered as Issei's children. And Trihexa has been giving birth to countless of Ise's children.