Honestly, I think the grandpa is not a good father to them... For me he seems distant and pretty quick to anger, not to mention his favoritism toward Euigang. So it's no wonder for his children to turn out like that, especially the aunt. Misogyny can also be seen in this manhwa, especially in the novel, women who are not talented enough in martial arts are not given the opportunity to explore other paths than to be married off. She also constantly got compared to Euigang. Thus, resulted in her never feeling secure and is willing to gain her position through illicit means. But I think her fault is the fact that she succumbs to her insecurity and directs her anger to Yeon instead of Paehyuk. I will never agree to harming children under any circumstances no matter what kind of insecurity she has.
Why are none of Yeon's uncles or aunt any good? How come her father is the only worthy child in the Baek clan? Why were the other children not taught any manners by her grandfather? And the same goes for their children as well.