User blog comment:B214/New anime 2017 discussion blog/@comment-97.86.117.132-20161230234256/@comment-87.8.65.225-20161231132829

Akeno and Rias bet on which one of them would have deflowered Issei first and which one of them would have been left pregnant first. So I guess 1-1 (Rias took his virginity, Akeno his child) lol [And Rias's son should be the sixth, at least looking only to the ones who appears, because only half of them are fighter, others chose to not become fighters. If I remember correctly the order is: 1) Kurenai Himejima; 2) Airi Hyoudou; 3-4-5) Zen Quarta-Shin Shidou-Helmwige same age; 6-7) Ex Gremory-Robertina Hyoudou same age; 8-9)Shirayuki-Kurobara same age, same month, same day (threesome with the nekomata sisters and both of them left pregnant? Issei is a semenator XD); ?) Ernestine's age was not supposed]

Well Ex is already able to kill gods and Airi scares all her brothers (including Ex) with her overwhelming presence that paralize them, so I guess there are not many doubts.

Kurobara and Shirayuki were the youngest of the childrens sent in the past (12-13 years old more or less).