I had an imaginary sister. An identical twin named Yolanda. She was the rambunctious one, the one who always got us in trouble.

“Who ate the cookies?” my father would ask me as I brushed crumbs off my lips.

“Yolanda, of course.”

Sure, I played with my two younger brothers, but Yolanda was who I had the most fun with. We’d walk over to the train station near my grandparents’ family hacienda to put coins on the tracks and watch the train’s tires flatten them as it zoomed by a couple of feet away from us. At that age—maybe five or six—I had no clue where my sister had come from, but now I believe she existed only for me to cure my loneliness. Over the next few years, Yolanda came and went until she slowly faded as I made new friends at school, even though I was sure no one would ever replace her.

Then, when I was ten, came the miracle. My brothers and I were preparing for our First Holy Communion and, as was customary for parents, my mother asked me what was I going to pray for when I received the sacred host.

“A sister,” I said without hesitation.

“You’re supposed to pray for peace on Earth, not make wishes,” she said.

But I could not be dissuaded, and my persistence paid off nine months later when my mother came back from the hospital carrying a little bundle and said, “Meet your sister Alejandra.” I was eleven then, and having a baby sister was far better than concocting an imaginary twin (sorry, Yolanda!). I immediately put away my dolls and assumed the big sister role with gusto. I changed her clothes several times a day, whether she needed it or not, enduring my mother’s reprimands. I bathed her, most times unsupervised. We slept together, unbeknownst to our parents. I fed her, don’t ask me what, but today her immune system is top notch. I was there when she walked her first steps, when her first tooth cut through her gums, when she ate her first mouthful of rabbit manure, when she showed up with a panty liner stuck to her cheek just when my boyfriend and I were kissing on the couch. She was probably four years old when I took her to see Romeo and Juliet, a movie that had been forbidden by my parents (“There’s a flash second there where you can see Romeo’s behind!”). Of course, we got busted and were grounded together, thus becoming mutual accomplices in all our adventures, which we remain today.

My sister and I call each other “Heerm,” which is a shortened version of “hermana.” We have no secrets from each other. I am the godmother of her four kids because she didn’t want to deprive any of them of the honor (her words). When I got sick with breast cancer, she flew to New York and camped at the hospital 24/7. I am her perpetual student in motherhood, common sense, friendship, character, spunk, loyalty and the meaning of family. Claudia, Olivia and Patricia are composites of us, with a good amount of fiction, a sprinkle of Yolanda and a dash of other sisters in my life. If asked, I would say that what I’ve learned most from my Heerm is that sisterhood is not a right, but a privilege. And this is what I wanted to celebrate in .