No, I only just caught up with that fact too. I'm assuming you're also used to how usually the bad moms in these type of historical shoujo/bl fantasies are female with a perma-frown.
He falls into that type of snake in the skin of a mother figure cliche, but with a twist that he's actually a male omega which makes his character design unique in a way.
Yeah i thought that manhwa team changed his gender since the fairy king in novel also became fairy queen in manhwa. After reread, i realized he actually still male omega yay (idk about the fairy queen tho). His outfit with big puffy sleeves and lace, including his long hair really designed very well, since in novel he hold the title as the most beautiful omega in country.
Not me just realizing that MC's "mother" was a man. It's not until the grandfather called him his son that I saw the flat chest. Was I the only one ? :O