The relationship between sisters is quite special. Your sister is the best friend you've ever had or could ever have. Two sisters fight like cats and dogs, yet at the end of the day, they are each other's favorite person.
When I was born, my mom hoped that I would be a girl. This is because my mom never had a sister and she wanted her children to experience a sister-sister relationship. Sisters can do everything and anything together. From playing with dolls, to bar hopping, to standing at your side on your wedding day, they are with you at every step of life.
Sisters are best friends. My sister is my favorite person. Ever. And I have met thousands of people in my lifetime. I don't know how I would've survived life without a built in friend to go on scary roller coasters with me, or to teach me how to survive school. Who would be around to go with you on spur of the moment shopping trips? Who could you rant to about your parents? Who would go on trips and vacations with you? Who would help you study for that exam tomorrow morning that you've been freaking out about? Who would have sleepovers with you just to watch Full House all night long? Who would share their Netflix account with you? Who would meet you at Starbucks before or after class?
I can't pinpoint the exact reason why sisters have such a special bond. It's just a feeling. No matter how many times you hit, scream and claw each other, or beat her up with a hairbrush, you just can't stay away from each other. Your sister is your sidekick and your special person. It's not just words when I say, my sister is my best best friend and I love her more than anyone I know.