1. You never had to wait for the school bus alone, because she was always standing right next to you with her oversized backpack and the lunchbox that matched yours.
2. She’s the first and only person you will quote The Parent Trap with.
3. You never left one another’s sides when you attended summer camps, birthday parties, or playdates. You walked around the entire time holding hands, and if you lost contact for even a second, you had a mild panic attack.
4. You never had to worry about your weekend plans. Because even if you didn’t have any playdates or sleepovers lined up, you knew you could hang out with your sister and eat popcorn on your parents’ bed while watching the latest Disney Channel Original Movie.
5. The first time you heard the phrase “attached at the hip” was when some grown-up used it to describe you and your sister.
6. You had no idea that the ugly faces you guys used to make each other laugh in church would eventually translate into adulthood. Only this time, it would involve you sending her two-second Snapchat pictures of your heinous face, and vice versa, while crossing your fingers that she wouldn’t be able to capture a screenshot of it.
7. You always looked forward to her sleepovers or birthday parties, because it meant that you got to get in on the fun too. And the best part was when your mom let you pass out the goodie bags at the end.
8. Christmas sometimes felt like you got double the presents. Since you and your sis played together every second of every day, her toys became your toys.
9. …which meant that when it was her birthday, it also felt like your birthday too, with new Barbies and dollhouses galore.
10. You always banded together on Blockbuster Movie Nights, so that you could convince your mom to let you rent both Jungle 2 Jungle and Angels in the Outfield.
11. You never got bored when your parents made you tag along to dull adult parties, because you always had someone to play with in the basement until it was time to finally go home.
12. …and now that you’re older, you get to go to family weddings rather than boring adult parties. And instead of playing in the basement together, you’re taking tequila shots at the open bar and embarrassing your mom.
13. You developed some of the weirdest, craziest, most imaginative games with your sister on long car rides or rainy afternoons. No matter what the circumstances were, you two always found a way to entertain each other, for hours on end.
14. You were always strategic during a trip to the movies. If you got Twizzlers, she got Raisinets, which meant you both always got the best of both worlds by splitting them half and half.
15. She knew your favorite Beanie Baby and you knew hers, and most of the time, you made sure those Beanie Babies were best friends.
16. Whenever you had a bad day at school, you comforted yourself with the knowledge that she was only a few classrooms away, and you could go hang out with her as soon as carpool started or you got on the bus.
17. Even if you didn’t share a room, you might as well have, since the two of you ended up in each other’s beds half the time anyway.
18. You know that in addition to being your first real friend, your sister is also a guaranteed lifelong friend. Regardless of how often you talk or how far away you live from each other, you know that you’ve got someone who will always stay by your side, someone who will always be honest with you, and someone who will always pick up the phone when you call.