Sisters come in all shapes and sizes. More often than not, they're full of mischief too. You and your sister can be the greatest of friends one minute but the worst of enemies the next - which is totally normal. If you have a sister, then you know for a fact that each one of these 18 things are true:

1. She knows exactly what you're thinking

Even when you don't.

2. When Mom isn't home, she is the bossiest boss of the house

Oldest or not, your sister is the boss of the house no matter what (sometimes she can also be the absolute worst).

3. Your closet is her closet (or so she thinks)

Sometimes things just go missing. When you catch her wearing your clothes, she better run...and fast.

4. People have told you two you look alike for your whole lives

No. For the last time. We are not twins. We are 2 years apart.

5. Your scrapbooks and photo albums are full of matching outfits

Even though we aren't twins, Mom would sure like to think we are.

6. You've got each other's backs no matter what

If your sister needs help, you'll be there to help her out and she'll be there for you. It's part of the sister code.

7. Don't embarrass her in front of her crush

It's rule number one in the sister handbook. And most especially, DO NOT tell him she likes him!

8. She makes the best cookies

And cakes and brownies and treats and everything else. She's got a baker's touch.

9. The sass is strong between you two

Nobody comes up with witty comebacks than she does.

10. It doesn't matter how long you stare at each other, someone will start laughing

Mom may think it's punishment to make two angry sisters stare at each other, but sure enough, in a matter of minutes, someone is going to crack and end up laughing hysterically.

11. Your parents tend to compare you to her (no matter how hard they try not to)

Sibling rivalry problems.

12. You're basically the complete opposite of each other

Just to start, she's an introvert and you're an extrovert.

13. She is the easiest and funniest to tease

There's only one person who can get under her skin and it's you.

14. You know exactly what makes her happiest

Years of living together will do that. You know every little thing there is to know about her.

15. She will always remember your most embarrassing moments

Hey remember that one time...?

16. You'll always be there for each other

Through thick and thin, until the end of the line.

17. Her opinion is the only one you care about

No matter what anyone else says, your sister is the only one you'll listen to. Her opinion matters the most.

18. Nothing could ever come between you two

She will always be your sister, no matter what. If you know one thing for sure, it's that life would not be the same without your sister.