For your question in my story Kissed by four brothers
The part -"No," Ezren interrupted gently. "Demons can't reproduce with humans or half-demons. It's... biologically impossible. You're safe."
Your question and comment-That makes no sense if her father was a demon, and I’m assuming her mother was a human. Then they can reproduce with humans and half-demons.
*My answer*-Lavana isn't a half-demon. She's a FULL demon — both her biological parents are demons. And not just any demons. They were the original leaders of Hell. The oldest and most powerful bloodline. But they committed a past sin and were bound to their duty forever. The only way to be freed was to produce a new version of themselves — a child who could inherit the burden — and then they died. The mother died because that's what happens, and the father died from punishment. Lavana was sent to the human world disguised as a human with fake human parents who later died in a normal accident. That's when Hell sent the four guardians to protect her until she comes of age and her powers fully awaken — because she's meant to become Hell's next leader and commander.
So when Ezren said demons can't reproduce with humans and half-demons — he was only speaking about the four guardians specifically. He never said anything about full-blooded demons. That assumption was the twist being set up
Please please PLEASE don't spoil this for other readers! "