I'm glad that in your case your husband's grandparents came to accept you and love you. As you said, they probably are great people. Just curious -- Were they ever rude to you in person in the beginning? Your husbands parents -- how did they accept you? Did they accept you right away, or did it take awhile? How did they react to the engagement?
A very big for you AutumnWind, I am so sorry that you fell into the other category of having terrible IL's who inspite of trying your best with them it's just not good enough. It is so sad that they are so blinded that they are missing out on a wonderful, loving relationship. Kudos to you for encouraging a relationship between your children and them, even though your MIL and SIL do not deserve it. I don't think I would be so patient myself, especially if they tried to manipulate my children.
I have an Aunt who sounds just like your MIL and SIL and if they are anything like my Aunt it's not so much about cultural differences as it's simply about pettiness and jealousy.
My widowed Aunt has only one son and he lives in another state probably to be far away from her. When he started dating a girl and my Aunt few out to meet her (she’s Caucasian) I knew before she even left that she wasn’t even going to give this girl a chance. It seemed like no matter what she was going to find a reason to reject this girl for whatever reason she could dig up and all reasons were petty and hidden behind a manipulative veil of concern for her son. Last year my cousin brought his girlfriend to our family reunion and my Aunt’s rudeness and dislike for her was so barely disguised that we all took notice (and tried to make up for it, because we all adore her and clearly could see my cousin’s happiness). A few of my family members even tried to talk to my Aunt very gently about it, but it just made her hate her son’s girlfriend even more. Now that my cousin and his girlfriend want to marry, my Aunt is playing little manipulative games, basically a power play. But luckily my cousin isn’t the type to respond to it, but unfortunately he’s not the type to call her out on it either. His way of dealing with the situation is seeing/talking to her as little as possible and living far away.
I imagine my Aunt would probably reject any woman my cousin brought to meet her Chinese or not. She’d probably have some different excuses, because she tried to manipulate me with my DH when we were engaged. She’d tried to manipulate me in little ways, telling me that her friends thought my DH wasn’t handsome/rich/tall/educated enough and thought that I could do better. I was flabbergasted and I couldn’t very well respond because the way she did it was indirect so I couldn’t accuse her of anything because it was her friends that said it. I just shrugged it off and told her I was happy with my choice and that her friends don’t know my DH like I do and that he’s was the best of the best of men.
I was very pissed though because when my Uncle died (I’m the only one who lives by my Aunt, the rest of my family is on the West Coast) my DH helped clean, organize and move my Aunt out of her house. My DH busted his butt to help her out (because of me) and she didn't appreciate any of it. My DH is also a handy guy that when something goes wrong at her house we get called so he can fix it. It got to the point that I got irritated and simply didn't want my DH used like that so that I’d just deflect her calls and come up with excuses that he couldn't help her out.
We haven't written her off either, but boy would I like to sometimes because she can be a real jerk about stuff. But we very rarely see her and most times I'll just go see her without him.
I would imagine that your MIL and SIL would be hell on wheels for a Korean DIL because like you said they are just difficult people and probably thrive on games like this. The other sad thing is because you're not Korean with Korean family to back you up, they probably feel like they can get away with a lot more. Hopefully your DH has some Korean family members who are kind and nice.