I wear a silver band on my wrist, engraved with the words: “Sisters: Forever Friends, Close at Heart, Make You Smile, Make Life Better, Share Hopes, Fears, LOVE, and Tears, Confidante, Soul Mate,” and “Are Fun.”

My younger sister bestowed it on me last Christmas after I wrote a letter to her and my older sister, lamenting over what I perceived as a corrosion of our siblinghood.

I’m the middle child, with two brothers, two sisters. Our childhood modeled the typical spoiled American brat pack. We five bonded over heaps of privileges our parents piled on us, and by circling our little wagons against their strict discipline. Beneath our family roots ran a deep current of such kinship complexity that we never gave it voice, yet often acted it out.

As genetic bonds loosen, and chosen bonds grow in strength, we learn to celebrate the connection between biological family and chosen family.

Although we never really fought, we squabbled. While quickly dismissing our sandbox standoffs, when a sibling hurt my feelings, the memory furrowed deep into my vulnerable brain.

Eighty-five percent of the brain’s development occurs before age eight. Parent and siblings’ interactions during these years lay down the neural framework that permanently informs our behavior, creating knee-jerk reactions in later years. We can modify our behavior by laying down new neural pathways that expand our psyche’s options, but the basic framework is permanent. This is how powerfully our parents and siblings affect our entire lives.

We siblings exchanged pranks. I recall: my older brother age 5, me 4; he’s offering me a bite of his maple bar. Yum. I bite down on a bar of Fels-Naphtha soap.

Siblings: The First Tribe

We fiercely defend one another: After school one day I chance upon my older brother pinned down by a hulky eighth grade classmate because my brother, not he, won a soccer award.

Being very small, when I approach, I don’t present an obvious threat; so the bully keeps bashing my brother, who’s fighting a boy twice his physical size.

I sink my teeth into the bully’s leg, piercing his trousers, then his skin, holding fast like a rabid dog until my brother rises to his feet. The bully slinks off. My brother and I walk home together in silence.

We never speak about the incident. If we did, I’m guessing our narratives would differ.

We loyal five conspire against the power structure that denies us individual voices: Our parents often seem overly authoritative. Perhaps we mistake protectiveness for brandishing implicit power.

We can depend on our older sister to defend the rebel fort, while our “baby” sister, whom we all agree enjoys special “spoiled rotten” status, notoriously sides with the current benefactor of ice cream cones. We five never — ever — snitch on one another.

We bond tighter: We invent a secret language and speak it at the dinner table. “Leaf” decodes as “Gene Autry.”

When at age 7 my younger brother is diagnosed with a genius IQ, I ask our mother what she and our father plan to do about the prodigy. My mother replies crisply, “Nothing. He’ll be raised like a normal child.”

I point out that by age 4 he played the piano by ear. He’s reading our older brother’s physics books, hiding them under his bed. My mother scoffs.

I assume our parents told my brother what the doctors told them. He meets the shore of madness. I don’t know how to help him when the tumultuous seas that can snare a child genius toss him onto the alien shoals of a normal world whose language he can’t speak.

My brother first learns of his intelligence quotient in his mid-30s, when I mention it offhandedly. His eyes reflect terrible surprise, then flicker like a fast-forwarded film of all the years he’s struggled with what made him “different” and set into motion the puzzling chaos that he courageously conquered.

At this moment, for the first time in my life, I feel I have betrayed one of my siblings. Why hadn’t I told him when we were children?

Over five decades our little wagons have taken different paths. We no longer circle them, nor share the same day-to-day routines, family rituals, even celebrations, except rarely. From separate experiences we’ve generated different philosophical outlooks. We’ve produced, or not, our own genetic offspring — new families.

From Birth Tribe to the Bigger World

The passing of the last parent marks a watershed in how we five relate to one another. Our last common denominator suddenly dissolves, or so it seems to me.

The fabric of our specific family grows neglected and frayed. Contact declines. We emotionally disperse. Today, we seldom visit one another.

Not all families experience disintegration of the center. Many siblings remain closely connected. These families seem to celebrate their bond every day of their lives. Why not us?

The beauty of nomadic families is that we savor every moment of our meetings, wasting no time on petty drama or profound animosity.

For the first time since childhood, we five siblings live within a few hundred miles of one another. I long to gather us together, celebrate our sibling-ness, whatever it amounts to today. Laudably, our “spoiled rotten” sister this past Christmas presented my older sister and me with the precious silver bands. There is hope.

But I wonder: If I throw a party for just the five of us, will anyone come?

Enter the new “chosen family.” Tribes of friends we gather as adults become surrogate family, perhaps improving the model. What I learned from my original family affects my choice of spouse(s) and also informs my selection of close friends. Whether identical to my original siblings or parents, or exact opposites, when I select new family my brain shouts advice from that toddler’s neural foundation.

Global nomads like me are content to bump into our selected siblings at the occasional caravanserai, picking up naturally where we left off, our bonds as strong as ever, as if only a day had passed since we last met. The beauty of nomadic families is that we savor every moment of our meetings, wasting no time on petty drama or profound animosity. Often we long for one another, yet we dare not settle down together.

Most chosen families reside within a few hundred miles of one another. Nomads or neighbors, it’s the old circling our little wagons with a new twist. Ejected from the original nest, we sculpt and shape our new families to fit what we need in order to survive.

Selected families nurture with camaraderie, shared meals, loopy adventures, close calls, gifts of time and tenderness, empathy, loyalty, bonding, and genuine sibling love. They are damaged by reenacted sibling rivalry, petty squabbles, jealousies, and ugly gossip.

Signs of unhealthy family circles include rule by narcissism, manipulation by drama kings and queens — the “it’s all about me” tyrants — meanspirited gossip, rivalry, and poisoned family politics. If this sounds a lot like the original family, there’s a good explanation.

There ought to be a Match.com for choosing siblings and parents.

Like genetic families, selected siblings and parental figures form a pecking order: authority figures, nurturers, sisters and brothers, at least one prankster, and sometimes, the shunned, who may cling to false threads of hope that the shunners will deem them forgiven, worthy of welcome back into the fold.

When a selected family develops animosities worse than original sibling rivalry, toxicity develops. When, say, a drama queen perceives her survival threatened, she’ll slam her wagon up against perceived rivals, declaring them shunned. Faced with a similar fate, chosen siblings either freeze or self-confidently circle their wagons against the queen’s injustice.

Tension reduces the tribe’s survival odds. As stormy relations intensify, disgusted siblings break off, seeking out new arks whose smoother sails enfold friendlier breezes, raising the personal odds of survival.

Beyond Emotions: The Real Reason for Our Chosen Family

While biologist E.O. Wilson conjectures on the need for “altruistic communities” among species of ants and avian, we humans ingeniously and constantly modify our chosen families in an ever-evolving process of family patterning that nourishes and sustains its connections, emotionally and even spiritually. Selecting siblings, Wilson would argue, is about individual and group survival.

Personal survival often trumps group survival to the detriment of the family. We select friends we believe ensure our survival.

We are a social species; we find hermits unsettling. Most of us need the safety net of a family circle, whether close at hand or scattered across the globe; nothing hurts more than being expelled from the group.

There ought to be a “Match.com” for choosing siblings and parents.

The upside of chosen families holds so much power that even an earthquake could not render it asunder. Our survival DNA is programmed to altruism, with notable exceptions, and we are such a desperately compassionate species that we tolerate, often indulge, one another’s weaknesses. And here’s the Achilles heel of altruism, fooling us into thinking what we just offered our sister is a bite of our maple bar when in fact it’s a mouthful of potentially fatal Stoddard solvent.

Within our family we feed our hungry and tend our sick. At times we collectively reach out to perform acts of love toward total strangers, the ensuing benefit an intoxicating elixir that nurtures our bond.

Like the circles of the Olympic Games, chosen family circles fuse until an endless chain loosely unites to produce the uncanny six degrees of separation.

The key to successful survival of a family circle is simple: human kindness.

Thus we bond, our connection stronger than Gorilla Glue, fierce loyalty ensuring our mutual survival. Thus we learn by action the true meaning of love, why giving feels better than receiving. What better achievement could we hope to celebrate?