I'm not sure myself but I think as long as it's a royal, that person can impregnate or conceived a child. It says as "bearing the blood of the imperial family, through sex, can conceived a child of their own". I'm nit sure. Try checking it.
http://www.mangago.zone/read-manga/who_s_your_daddy/uu/mpn_chapter-2417722/22/
well nothing rly happend tbh, He fainted and the doc said he's pregnant (Somone royal) than he goes to the ball with he's sister i think, he meets the prince and they talk about the murderer and the prince kisses him and leaves a mark than the mc runs out. And he meets the duke outside, the duke asks about his response cuz he confessed to him 4 months ago (the time where he got pregnant). The mc thinks the father is the duke. And than there r some newspaper about the prince and mc next day (being in a relationship or something about rape cuz he left a mark and the mc was a lil undressed). And than the mc meets the prince and he talks some shit about him being a white cat or something, flirting or something. He gets all jelly jelly cuz he smelled a woman on him or sum. They made a deal, the prince has to help with the case of the murderer and the mc has to sleep in his room for some houres i think. And than the new chapter comes ( ̄∇ ̄")
Sorry I know there's not a lot of chapters but I am confused on the story. All I understand tbh is that MC (knight) is pregnant from a one night stand with someone he doesn't remember, and that royals are the only one that can mpreg? Could someone please give a recap on what's been happening so far?