Me and my two sisters didn't get along as kids (one is 18 months older than me and the other is 4 years younger). Once we became teens, my older sister realized I was standing up to the people who were bullying her at school and we became closer. I became closer with my younger sister when she started high school and I was going through the process of planning my first wedding.
We've been there for each other through marriage, divorces, miscarriages, birth of our children and so many other life events. While we don't see each other often, it's known that any one of us would be there for the others in a heartbeat.