User blog comment:Lias' Pawn/Issei's possible further Harem members/@comment-1359322-20150111001048

Yasaka, well she's the leader of the Youkai, she has a daughter. So we can't exclude the fact that she might have a husband, just not shown or mentioned.

Serafall. She's too much of a sis-con to fall in love with Ise unfortunately. She can nosebleed to Sona acting cute, and she just can't seem to get enough of it, Sona is 18, that means Serafall had 18 years to try and get use to Sona's cuteness but she can't. Too powerful of a sis-con. And like Yasaka, we can't deny the fact that she might be married already. All of the maous are around 200 years, they might be married and have children already.

Seekvaira, she's going to be the Agares Clan head. Like Sona, she isn't going to end up as a candidate. I don't think any Devil would like for their clan head to be a mistress of someone, or the fact that their leader's husband having to carry the name behind the name of another clan like they are inferior to them. If Issei Gremory Agares, the Agares won't be happy, if Issei Agares Gremory, the Gremory won't be happy. Hey if Rias is proud of her "Gremory", do you think Seekvaira isn't proud of her "Agares" name. I don't think they'll accept being seen as inferior to another clan.

Gabriel. No, i don't view her as a good candidate. She's a member of the top brass of the angels. Plus there might be another huge revolt just like the one in Volume 19, because of jealousy. And the worst is it might come from all three sides of the Angels, Fallen Angels and Devils. Also regarding "why did the Author have Gabriel as a beautiful woman in the first place if he was not planning to have her be in Issei's Harem?" If a go base on this logic, every girl in DxD should have gone to Issei already. Not just Gabriel, but Grayfia, Serafall, Sona, Tsubaki, Sitri Girls, Seekvaira, Riser's girls, Venelana etc. So being beautiful has zero relations to being a part of Ise's harem.