1. When people see photos of her they always remark on how you two look alike. Usually when you're not even in the photo. They just see her and think YOU.
2. You have also been told you have the same facial expressions. People notice this at group dinners because you are equally incapable of hiding your true feelings even without saying a word.
3. After being told you look alike so many times, you also start to realise she has the same vocal intonations as you. You somehow slightly shriek at the exact same moment in your exclamations.
4. Even though you haven't lived together since you were both in high school, you still basically have the same likes and dislikes. You've tried new stuff since you moved out but still, you don't want to go camping and you can't deal with the cold. These are the core values that bind you as family.
5. You wear the same clothes without planning it. When you're on holiday together or visiting her you realise she went to Zara and bought the exact same cobalt blue tank top you just bought at Zara. Great minds, etc.
6. Facebook's auto tagging tool always wants to tag pictures of her as you, or the other way around.
7. Your relatives always confuse you two. Like, your aunt always says her name when she means your name, or vice versa. You thought this habit would expire once you were no longer kids, but alas.
8. Even your parents sometimes think you are her and she is you when you call their caller ID-less landline. Because you have pretty much the same voice and say "hi" in exactly the same pitch.
9. You text each other the same thing at the same time. Re: family drama, something hilarious your mum just said in group text, or even just someone from high school's annoying Facebook status.
10. Your man always asks for her help planning things for you or buying gifts for you because he knows she wants the same things you want. If he's proposing, there is no way she's not getting a phone call.
11. You have the exact same hair type. So you can always talk about your hair idiosyncrasies and the best hair products to tame it. More importantly, when you visit her you don't have to pack that shit because she has all of it.
12. Since you grew up with the same pets you love the same animals, which means she's always there for you when you just want to enthuse over the meme of cats sitting on glass, or whatever.
13. The same random things make you dissolve into laughter. Which is funny because you have the exact same laugh.
14. Your sister's kids (if she has them) or pets (ditto) have been thought to confuse you for her. Her cats like nobody but your brother-in-law is convinced they like you because they think you're her.
15. If she's married, her wedding was exactly the wedding you want some day. You both get turned on by the same centerpieces, what can you say?
16. You both know that no matter what kind of shit the other gets in, you will be there for her in a split second, willing to lay down in traffic if that's what she needs. Because sister love is unbreakable - no matter HOW much you annoy each other sometimes.