Growing up with a sister is like growing up with a built-in best friend. No one understands you like your sister does. She understands your crazy family, your quirks, wonderful parents, and she knows the intimate details of your life. She knows your moods, when to avoid you, when to make you laugh and when all you need is a friend. Sisters are the best gift that your parents ever gave you.

1. Every road trip turns into a concert experience.

Whether you're driving cross-country or just to your local McDonald's, getting in the car means it's time to jam.

2. You tell each other everything. TMI or not, she must be informed.

Pretty much nothing is off limits. Stomach issues? Weird rash? Better ask her.

3. You fully embrace each other's oddities, no matter how strange they are.

You know that she can't sleep if heavy blankets make her legs feel too restricted, and she knows that you prefer to wear socks 24/7. She drinks chocolate milk with every meal, and you have weird OCD tendencies that she accepts and tries not to exacerbate.

4. People refer to you as "the girls" because you're almost always together.

Family and friends always invite both of you. If they invite one of you to an event, they know they've invited your sister by extension. Why would you go somewhere without each other?

5. Full, or even coherent, sentences are not necessary.

You always know what the other is talking about, even with the worst explanation possible. "Can you play that one song? You know, with the singing and the beat?" *She plays the exact song you were asking for.*

6. She can make you angrier than just about anyone else.

But of course, you never stay mad for very long. If you don't make up, how will you show her the hilarious video that you just watched?

7. You have the exact same sense of humor.

Even if no one else in the room is laughing, you look to her and you both crack up. You have countless inside jokes, and no one else will ever be able to laugh with you the way she can.

8. You never stop teasing each other, even when she gives you "the look."

From pretending to tip her over in the recliner to telling her to "settle down," you never pass up an opportunity to mess with her. You both think it's funny. Most of the time.

9. You can always count on each other.

There's pretty much no one you depend on more. Your parents are driving you crazy? You and your boyfriend are fighting? You go find your sister.

10. You couldn't live without each other.

Above all else, you know you couldn't live without your sister. Whether you live in the same town or across the country, no matter what is happening in your life, you always remain close. She's your very best friend, and you never want to be without her. Or more than an hour away from her. Maybe you'll just live together forever.

Dedicated to my very own little sister, Lydia. Happy birthday!