My sister is 2 years older than me. When we were tots, I followed her around and copy-catted her every move....like any little sister would. I wanted to be "just like my big sister". We were fairly close up until we hit the puberty divide. All of a sudden I became the "weird little sister who tags along" and she was interested in herself and boys more than me. I have distinct memories of feeling hurt by this, I just didn't understand why my big sis didn't want to be my friend anymore and we began resenting each other for a few reasons:

We are both similar looking (same height, hair colour, both have light eyes and dark har) but we have always had very different styles and personalities. My sister has always been more 'looks' driven, wearing lots of makeup and dressing "sexier" - she was always the "good looking sister" (as told to me almost daily throughout middle/high school by my peers) and I was made out to be/feel like the average one. This, of course, made me resent her - nobody wants to feel like the subpar version of their big sister. I spent most of my high school days feeling inferior to her. She was always the irrespondible/wild child and I always hated feeling like I had to get the short end of the stick and do everything right because I had to make up for her shortfalls. I spent a lot of time feeling like "why do I have to do this, YOU'RE the big sister!?!" I would lecture her all the time and get angry at her for anything she did because I felt slighted. We could get along for short periods of time, basically out of good manners, but we fought constantly to the point of just staying out of each others way.

To this day, I am still definitely the responsible one......but maturity and life made me realize that I never HAD to be in that position. I also learned that my sister and I are two completely different individuals. I spent so much time thinking that my self worth/how people perceived me was in contrast to her - that somehow she was the level I had to measure up to.......but than I realized that nobody is comparing us, we are our own people. Once I came to terms with that (along with some geographical space), my sister and I have become really close friends. We balance out each other and are able to give great advice to each other. We'll never TOTALLY get along, but we respect that we are each others yin and yang and I wouldn't give our relationship up for anything.