SandyTree's manga / #Princess(4)

https://m.qimiaomh.com/manhua/5024.html Current 39 So the dukes family has an issue with conceiving. In order to have a son both parent must be related. In order to have a daughter the women must have been purified with mug worth before her menstruation becomes regular or whatever then take the herbs/ cure for a year. She also would have to been a virgin and only have been with a duke. The dukes brother didn’t know that he fell for his sister. She was abandoned outside after their father found out she had poor health. He also didn’t know she was pregnant. I think the doctor has something to do with them meeting I’m not sure. The duke thinks the only way to have a kid outside of the incest is this weird thing like “drinking blood of Lucia” or something the doctor told him as a lie in order to deceive him. So any children of Lucias would be female and the only way for the nephew to have a son and pass on the name would be to marry Lucias child. Which is what the doctor later wants( hence the lie to the duke about the blood) He plans to have the son/ nephew marry the daughter in order to pass down the bloodline.