Family will not accept children

I am a single mom by choice. I have a daughter, 6, and a son, 3. Until this year my twin sister and I were very close. In fact, I relocated to another city for the sole purpose of being near her. I wanted our kids to grow up together and bond as cousins. We have daughters the same age. Moving to my current residence was mostly my sister's idea. I was a little dubious about it because I left a city with a very reasonable cost of living and moved to one that is exponentially more expensive. But I was willing to take the financial hit because I loved my sister. Then after we got here my sister decided she doesn't like my daughter and stopped having anything to do with us. Toward my son she is indifferent, I guess, but she really, really hates my daughter. So much so that she won't allow my little girl to play with her daughter. She thinks my daughter is a bad influence. My sister doesn't call me anymore. She doesn't visit anymore. The only time we see each other now is holidays, when we have to put up a front for my mother's sake. Other than that, there is no contact. My daughter isn't a perfect child, but she's no better or worse than any 6-year-old. She is learning boundaries but is generally respectful and well behaved. Two different teachers at two different schools have named her student of the month. She gets good grades. She's a lovable, sweet little girl. I know that my sister's issues with her are not in any way related to my daughter's behavior or personality. Nobody else in my family, nor any of my friends, have any problems with my daughter. My sister seems to be taking out on my daughter some weird control issues. She was opposed to me adopting both my kids and tried to talk me out of it. I didn't listen, obviously. I thought once we moved out here and she got to know them, my sister would bond with my children. After all, that's what she said she wanted. She's the one who encouraged me to move here. But ironically, instead bringing us closer, being in the same city has caused alienation that I fear is permanent. At first I was hurt by this, but now frankly I'm just angry. My brother-in-law is a jerk. Nobody likes him. But my whole family has just sucked it up over the years because that's who my sister chose, and if we want to be a part of her life, we have to be a part of his. But now the shoe is on the other foot. My sister doesn't want to be a part of my children's lives, so she's all but disowned me. I find her hypocritical and selfish. What ever happened to unconditional love and acceptance? Most importantly, I'm angry that she's hurting my children, who in their innocent ignorance have no idea how much disdain my sister has for them. They love their aunt. She at least has the decency to be polite to them when she can't get out of seeing them, which my kids misinterpret as love. They are always asking why we can't go over there and have a play date. Every day, I make up excuses. But one day I will have to explain to them the real reason we don't go to my sister's house anymore, and the truth is going to crush them. They will inevitably internalize the rejection as some sort of reflection on them, which isn't right or fair. Have any of you got relatives who won't accept your adopted children? How do you deal with it? Do you just cut those relatives out of your life entirely or find a way to shield your kids from them while still retaining some level of contact?