She teases you, supports you and is somehow your best friend and worst enemy simultaneously. She's your sister.

Sunday is National Sisters Day, an observance with no clear origin but an obvious goal: celebrate sisterhood. Whether you and your sis are like Mary Kate and Ashley Olsen, Anna and Elsa or John and Joan Cusack, Sunday is a time to reconnect. Pick up the phone, meet for lunch or send a greeting card to let your sibling (or best gal pal) know you're thinking about them.

Here, we'll even help you do it. Share one of these 13 quotes about having a sister, collected from Goodreads, the Quote Garden and BrainyQuote:

"She is your mirror, shining back at you with a world of possibilities. She is your witness, who sees you at your worst and best, and loves you anyway. She is your partner in crime, your midnight companion, someone who knows when you are smiling, even in the dark. She is your teacher, your defense attorney, your personal press agent, even your shrink. Some days, she's the reason you wish you were an only child." — Barbara Alpert

"Sisterhood is powerful." — Robin Morgan

"There's nobody in the world that knows me better than my sister." — Tia Mowry

"She's my little sister. Mine to torture and mine to protect." — Julia Quinn

"You can kid the world, but not your sister." — Charlotte Gray

"'Help one another' is part of the religion of sisterhood." — Louisa May Alcott

"I always like to win. But I'm the big sister. I want to make sure she has everything, even if I don't have anything. It's hard. I love her too much. That's what counts." — Venus Williams

"Because there’'s one thing stronger than magic: sisterhood." — Robin Benway

"When sisters stand shoulder to shoulder, who stands a chance against us?" — Pam Brown

"Siblings that say they never fight are most definitely hiding something." — Lemony Snicket

"You may be as different as the sun and the moon, but the same blood flows through both your hearts. You need her, as she needs you." — George R. R. Martin

"Being a twin, and being my sister's twin, is such a defining part of my life that I wouldn't know how to be who I am, including a writer, without that being somehow at the centre." — Taiye Selasi

"Is solace anywhere more comforting than that in the arms of a sister?" — Alice Walker