I believe he was impregnated due to Geumryang’s magic and because there was intent to produce an offspring. I don’t think they would be able to have more kids because there’s no real need for Geumryang to continue reproducing after the twins were born. It’s been a while since I read this all the way through and this is just my thought process on how it could work though
Geumryang placed a bead of sort in taesun's ass in the early chapters, that's why taesun could bear a child despite being a man, also that's what altered his body sort of
I love both of you; thank you for the kind breakdown and reminder !!
Wait, was it stated before that his womb was dissolved away or something? Can he not get pregnant anymore?