So, who bred best?
>That moment when you realize that Issei's sons can reach Oyakodon with one of their sisters and moms without actually committing parental incest.
She has very low birthrate. So she probably got cummed inside a lot more times, before she actually got preggers.
However, Ravel has the same excuse and she's before that.
But I can't blame Issei on that, the phoenix revives my dick
It was not revealed. Typically due time travels shenanigans they can't say too much about future.
But Kurenai in between line hinted that Azazel is no longer alive in future for some reason.