Having a sister is great! It's like having a whole extra person in your life you didn't even ask for, but you know you couldn't imagine your life without her. While you may fight occasionally, you guys are truly best friends who know each other inside and out. Here are 18 perks of having a sister.

1. You have a lifetime best friend.

She's your partner in crime, your go-to, and your "day one."

2. Her closet is your closet.

You always have two closets worth of clothes to choose from.

3. You can tell each other anything.

That cute boy you saw the other day? That time you accidentally drove your car into a pole? You can always tell your sister everything, from the good to the bad.

4. Her friends are your friends, and vice versa.

Extra friends to go on Starbucks runs and jam out to your favorite songs in the car.

5. You have your own language.

You two talk in this whispered, yet fast-paced, jabber no one else seems to hear or understand.

6. She will be your maid of honor.

You don't even have to think twice about who you'll choose as your maid of honor when you get married.

7. Telepathy

You always know what the other one is thinking and can telepathically read each other’s minds. There’s always that "OMG I was going to say that, too!" moment.

8. She knows you down to your core.

She understands you on a level no one else possibly could. She has the ability to detect even the slightest change in your mood and knows exactly what you need at any given moment.

9. She’s the best gift giver.

When it comes to birthdays, Christmas, graduations or any other special celebrations, she always knows exactly what you want.

10. She’ll cover for you.

She’ll help you sneak boys in the house, sneak yourself out, hide a pair of pajamas under the step for when you sneak yourself back in, have you on speed dial if your parents wake up and transform into a pathological liar if you get caught. She always has your back, no matter what.

11. You have a million inside jokes only the two of you will understand.

You have your own funny words, phrases and inside jokes no one else will understand except the both of you.

12. She's brutally honesty.

Not sure about that outfit you just threw on or the new boy you are crushing on? Your sister will always tell you the honest truth, whether you like it or not.

13. You always have a shopping buddy.

You know she'll always be up for a trip to the mall because neither of you could ever have enough clothes to wear.

14. She's someone you can completely be yourself around.

You can always goof off around each other and be yourselves without judgment.

15. Fashion advice

She'll always be there to tell you whether you look like a Victoria's Secret model about to strut down the runway or 2007 Britney Spears when she shaved her head.

16. You can make fun of each other.

You know all about her most embarrassing moments, and she knows yours.

17. Life advice

Don't know what to do about a certain friend? Is school stressing you out? You can always count on your sister for solid life advice.

18. She's someone to "pig out" with, without feeling guilty.

You two are always hungry and are up for any chance there is to go grab your favorite food together and shamelessly eat it, too.