MC's parents kept saying they don't want to marry FL to the prince but they keep missing the hints about the son's relationship with the prince. If they are really sincere in stopping it, they would pay more attention. The mother has already known the son had met the prince and he had positive impression of him. She really thinks that with her son's character, just pinching his ears would work. She sent people to monitor the son but they failed to spot the son getting closer to the prince. I thought there would be some trouble with that much monitoring, she was even worried about it but then all the people she sent suddenly gone from the plot. (I'm not sure if they will appear later but atp they are useless.)

He should be more vigilant with people he comes in contact with. He cares the most about his sister so he should have known that what he was facilitating could be mistaken as private exchange. If anyone finds out, it could drown the MC on spits. He keeps mentioning his sister to a foreign man and he did not at all suspect why the prince is too interested with his sister's affairs. He was already reminded by his parents not to ask for help from the prince about his sister's marriage as it would damage her reputation but he still did it later.

He left the disciplining to the mother as if his son would become a talent if they don't give him money or just give him cold treatment. His child's temperament has already been set. They are treating him like a child and not explaining things when he is at marrying age already. The parents are discussing relatives for the sister but the son at engagement age is still not bethroted. (Another problem with this plot, second sister actually got engaged first which in ancient times could affect the elder sister, here the FL, since the family don't value her enough. People will even more suspect that something is wrong with FL - that her reputation is true. I'm not sure why her parents did not make a fuss about it.) Back to the son, it seems like the parents have no plans to correct him at all. He doesn't want to see him in dali temple but he doesn't take concrete steps for it not to happen.

The mother knows the time FL will be seen by the prince. If she really cared, she would marry down rather than keep wasting her time looking for daoist priests. She could've bring the FL to social gatherings. She doesn't have a maternal family or bodouir friends at all? FL already said she only wants someone reliable but the mother has to look for someone higher than a son of a minister. She already knows it's not easy to match when climbing high based on how the second sister ended up in prev life but she is bent on marrying even higher. And the father just watched it all happen, no urging or suggesting other way to his wife. He already knows how close his son is to the prince and how s*upid his son is but he did not do anything until the prince approached him.