There was this manga i cant remember the name of. The mc is the best scientist (looks like a twink) in their universe and was running an experiment to make men get pregnant, and when his research was cancelled he tried it on himself using ml's sperm. At some point he runs away from ml because he didnt want him to find out that he used his sperm and the ml finds him. I remember he also had a very funny brother who's a doctor and the ml runs a company for medical equipment
Wdym the end they're part of my daily routine stop my babies