I have three daughters who are thirteen, seven and three years old. They spend an alarming amount of time complaining about each other, criticizing, bossing and generally being as annoying as possible. Last week my seven year old, Arabella, came to me crying about how she has no friends in the family (I also have three sons) and this is, for the most part, true. I have taken each of my other children aside since then and explained how Arabella feels and could they please, pretty please, invite her to the park or to play a game. They usually do and for a day or so Arabella is happier.

It’s only a matter of hours, though, until three year-old Ada loses some of her sister’s Polly Pockets. Or Ada breaks the Lego tower on India’s desk (let’s just gloss over the fact that I have a thirteen-year-old who spends her babysitting money on Legos). Or India and Arabella spend ten minutes quarrelling about who, exactly, owns the brown Webkinz dog. Or Arabella informs Ada that she is definitely not a good dancer.

Maddening, to be sure. Like every parent in the history of the world I have wailed, more than once, “why can’t you just get along?” Really! Why can’t they?

Let me rewind about thirty years to the house I grew up in. I was the oldest child with a sister three years younger. I loved to torment her. No insult was too awful. No slap too hard. I didn’t think twice about stealing money or candy from her room. Somehow that wasn’t bad because she just didn’t count. I don’t recall ever considering how any of it made her feel. I do remember my mother staring at me and saying through clenched teeth, “one day she will be your best friend.” That thought stunned me. My sister? Be my best friend? Out of the question. Simply inconceivable.

I continued to tattle. To taunt silently in the car so she’d get in trouble and I wouldn’t. To take full advantage of her kind nature and get her to take the blame for something bad that I’d done. Sadly, there were few, if any, kind moments between us.

Shortly after I turned seventeen, magically—suddenly, almost overnight—I liked her. Out of the blue. My sister was funny and cool and liked the same music as me. We weren’t exactly best friends, but I didn’t mind the twenty-minute drive to school with her. We’d go shopping on the weekends and I helped her get a job at the frozen yogurt shop where I worked.

The year she started college was the year I got married and moved to the other side of the country. As strange as it seemed to me, she was the person I missed the most. I begged her to visit for the holidays, and saved money from my menial little job for plane tickets. I can’t explain why, but it was as if there had never been any hard feelings between us.

She became my best friend.

She is the reason why, after I had my first daughter, I told my husband, “we’re going to keep having babies until India has a sister.”

And now India has a sister. Two of them. I look at those three girls as they find fault with each other and say unkind things, and wonder if the age difference is too big to be best friends. What if Arabella always feels like she doesn’t have a friend in the family? Or what if they just plain old don’t like each other?

I try to make everyone get along. I have said those same insane words that my mother said to me, “one day she’ll be your best friend.” I’m hoping it will be true. I’m praying that they’ll have the same happy ending that I did—the one I didn’t deserve, but so marvelously fell into my lap.

My gift.

My sister.