@justforthelulz@Richman@bowser_communist Assuming no twins/triplets and assuming each birth was 9 months apart wit no premature or late births, with no stillbirths or any other effects, that means it was about 9 years for them to have all of those kids.
@Tamerlane
Given that she's a witch, maybe she used magic to reduce the overall pregnancy time (let's say ~6 months each, so over the span of ~6 years).
@Richman
You want your goddamn doujins? Well, it's not a witch/human pairing, but it is by the same artist (Takla/Takura Mahiro). Also, NSFW warning ahead.