Who learns how to push our buttons (and we theirs) at an earlier age than our siblings? Most of us have family tales like mine. My sister, 21 months older, hit me over the head with a book when she was three because I wouldn’t read to her. I angrily pushed her down the stairs when I was six; I jammed a stitch ripper in her leg when she was twelve after she’d locked me out of the house. These stories survive even while the underlying arguments are long lost to memory. For my daughters, similar rivalry fueled the early years. When friends arrived to ooh and ahh over the new arrival, the older shook the baby’s crib, screaming that she wished the baby had died already. This came after a milder insistence, ignored by me as new mom, that we take the baby back to the hospital.

Time heals, and the bond grows. The older sister I assaulted is the one I’ll jump in the car for at the least provocation, driving five hours to share heartfelt conversation and dinner over a bottle of wine, and breakfast the next day before reversing my route on I-35. Ten hours invested in order to share six. At my younger daughter’s senior recital celebration this month, my older daughter offered a tear-inspiring toast full of praise and love for her sister’s talents.

Siblings, our first chance to learn to relate to others, are the peers we don’t pick to inhabit our lives, unlike spouses and friends. We define ourselves by seizing the open spaces in the family. She’s the cute one? Then I’ll be the smart one. You can’t play the French horn, because I’ve already picked that and want to defend my musical territory. I’ll be the good kid, since you’re the rebel. Degrees of freedom for decisions diminish with number of siblings.

Growing up with three sisters was immersed in camaraderie as well as competition. Melded by moving and month-long family vacations, we had no one but each other. Today, these three women are as important to me as anyone in my life. I live the research that cites the contribution of sisterly conversations to our happiness. During my early years of parenting, I yearned to live closer to my parents, needing their practical support. Now, facing the real permanence of the empty nest as my baby nears college graduation, all I think about is living closer to my sisters. A tough task, given that we’re scattered from Texas to Pennsylvania to Minnesota.

I never missed having a brother, until I realized recently that one dear friend talks daily to her brother who lives several states away. Perhaps I’d understand the opposite sex better if I had a brother to help unravel the curiosities of men (and vice versa, I’m sure.) The male-female relationship of siblings is free of the mess incurred with lovers, the never-ending question of whether men and women can be true friends. What an enviable wonder that would be.

A dear friend lost his brother this week, suddenly, leaving this friend as the sole family survivor. This unexpected death reminded me again of how precious siblings are, and what a hole there will be in my life if I survive my sisters. They are the human beings with whom our lives overlap the most: neither your spouse/partner nor your children share more years of your life. So I was glad to see that a national “Sibling Day” is in the works. The first was celebrated, unbeknownst to me, on April 10. I’m marking my calendar for next year, but meanwhile:

THANKS, SISTERS, FOR ENRICHING MY LIFE–then and now. I’d be lost without you all.