lulu is right. spoiler alert
so the "son" is actually his brothers son. if im not wrong it was the brother and sister son? but in the future, they will meet the son, FL doesnt know that it was his brother's son and make a good impression. the ML hates the incestuous line so he will end it himself and intend to make his nephew the heir. and if i remember correctly, FL and ML will be expecting another child. (づ ̄ ³ ̄)づ
Ok, so it said it the story that the sons were always born out of insect and daughters out of normal humans, so HOW DOES THE DUKE HAVE A SON IM SO CONFUSED????