Heartless in laws

I lost my mother a week ago and I'm devastated. I have always known that my sisters in law doesn't like me why I don't know. But I have attended their parents funeral and have always been polite but they did not attend my mother's funeral or came to see me. But because I'm a forgiving person I went to see her daughters newborn child and she was there. Her daughter gave me a hug and was sorry to hear about my mother's passing but my sister in law just said oh yes and that was it. My mother in law always takes their side and if it was the other way round she would phone and tell my husband. I know I should ignore them but it does hurt and I miss my mother so much