User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-4547267-20140619162357/@comment-82.48.188.251-20140619204331

If you think about it, Rias could really be the last to have a child with Ise. The pure-blood Devils have so much difficults to procreate (look Lord Gremory and Venelana: Rias and Sirzechs have hundred years of difference). Infact Xenovia said that as reincarnated human she can procreate early than pure-blood devils. Rias could be one of the last girl to be pregnant of Ise's child. It's more probably that Xenovia, Asia or Koneko could procreate (since they said that Koneko could have been pregnant even the first time that she was in love period if she had sex with Ise)