User blog comment:B214/Shin DxD 1 discussion/@comment-95.210.189.106-20180820141921/@comment-31137559-20180824170727

Every female living in the Hyoudou residence is in Issei's harem(well besides his mother). Every female in Issei's peerage is in Issei's harem.

Anything else is just speculation and wish fulfillment. Especially the adult women. Because it's highly unlikely any of them will join Issei's harem. So Tiamat, Gabriel, Yasaka, and Roygun are basically just what some people want. Grayfia is way more likely to join Issei's harem than those four.

Ones like Lint, Bennia, Kiyome Abe, Lilitifa Vepar, and Tsubasa Yura are understamdable. But some act like Bennia's already in Issei's harem.