User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-2607:FB90:4A8E:C500:80A:87B2:1048:97F3-20190609012154/@comment-38340421-20190615152534

The dxd ex isn't written in stone. Since in that it was only 12 waifus. But that was already changed in this volume to 15 plus. So with that alone he will have way more kids. Plus we weren't given accurate numbers to how many kids he has in that dxd ex story. Just the 12 main named kids. Plus even in that it was hinted at there were many more. But they were the most battle ready. Also saw a tweet that the author has plans for even Issei great grand son. By then Issei is retired and still has a high sex drive with Rias and the rest of his waifus. lol Which i think means he's still having kids even 50 plus years later XD. But at this point he's more or less retired and freed up time to spend with his wonderful loving waifus. :3