User blog comment:B214/Question and Answers 3/@comment-67.83.199.116-20140730041849/@comment-67.83.199.116-20140730045102

I get what your saying, I want Issei to marry everyone in his harem, but I always figured that Rias would be his first time and the first to give him a child (sometimes before their even married), and she would "relieve" him with both her love and body.