User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170331222853/@comment-31137559-20170401035556

Not that I doubt it, but where did it state that Lord Gremory had a harem bigger than Issei? And also Issei's harem is far from complete. So far he has 12 girls confirmed in his harem. And he is going to have at least 20 in his harem. Who knows how large Issei's harem is 30 years from now. Those extra children were most likely from Issei's other wives because we have to consider devils and their low birth rates though it didn't take Issei long at all to get them pregnant. But still, Rias having 4 children in 10 years is just way too much.