I have a crazy sister and she made communication with my parents who lived a continent away almost impossible. When they passed on, she and my nieces made my life miserable during the funeral time. They have gained my DH's wrath forever. I call her on holidays but never in front of my DH. She is my sister and she must be very unhappy with herself to be so ridiculous. She got mad at me for sending her a birthday card when her religion du jour did not celebrate birthdays. She said I was disrespectful. Who knew? She did not speak to me for 15 years. When my parents got older, it was like walking a minefield trying to speak to them. They had to call me when she was not there. I call her because I forgive her. She is my only relative left, except for those horrible nieces.
Luckily for me, I have a wonderful husband and two awesome friends who have the similar problems with their sisters and we get together and laugh and gripe about our siblings. It helps to laugh about it because other than that you will be crying and wondering what is wrong with YOU.