im think maryen's mum is a elf demon of some sort and maryen's dad is a purebreed human because its really rare for non purebreeds to get giantess prego so idk how maryen and kendra would be born close together unless they parents got really lucky or he is a purebreed human. and it took margarita's parents ten YEARS of trying just for one kid
It makes it harder but not impossible, giantesses have vastly longer lifespans so 10 years isn't that big of a deal for them.
Purebreed humans are also extremely rare , it's more likely that their parents fucked like rabbits until they eventually got lucky.
Speaking of purebreed humans, the story mentions that most of them reside in Timfalme. This could explain why Timfalme has so many more giantesses than the other kingdoms since purebreed males can impregnate giantesses much more easily.
It begs the question of whether Orphelith ever used it to her advantage, she could've incentivized purebreed males to impregnate giantesses in order to raise a massive army and overwhelm the other kingdoms with sheer numbers.
Then again, both Naya and Yakuu don't seem to care much about the MC being a purebreed despite the massive strategic advantage he could offer. While Naya is a bit of an airhead Yakuu is an accomplished general so she should've recognized the MC's strategic potential.
I know, I was just giving my guess as to why Kendra is a demoness but Maryen isn't. Everyone else is talking about how one of their parents must be a demon but I thought my guess was a little simpler.
But Maryen also has a "demon" side and she never visited Homaspersia as far as we know which suggests it's something genetic and not purely due to corruption.