Today, I turned 42.

For many, turning 40 is the big landmark, the official gateway to middle age. But for me, becoming 42 presents another sort of milestone.

One of my first memories was sitting on my parents’ bed when I was 3-years-old.

“The baby’s kicking, feel it,” my mom said. I pressed my small palm to her belly and waited. Something nudged my hand from inside her. “You’re going to be a big sister soon,” my mom reminded me, smiling.

A few months after I placed my palm on my mom’s stomach, my brother Will was born. He was a bright burst of blond hair and blue eyes, always camera-ready and providing pure contrast to my shy, dark-haired self. But I had seniority by virtue of being born first, and he tagged along, always lagging behind by those three years that separated us.

Until I was 24.

Will was 21 when he died from a lethal combination of heroin and alcohol. We’d been on the threshold of turning in the sibling rivalry of childhood for something closer to friendship. In his death, the life I’d known shattered. The sturdy table of four that had been my family became a wobbling, three-legged stool. And it wasn’t just my brother who was lost—my parents would never be the same. I would never be the same.

No one tells us how long grief can linger, how deeply it can permeate.

The first years after his death were a blur of shock and tears as I tried to comprehend that we’d make no more memories together. I wouldn’t be an auntie to the children he might’ve had, and there’d be no one else who knew what it was like to grow up in our particular home with our particular parents. He wouldn’t be there for our parents’ health scares, the death of our grandparents, or anything else.

No one tells us how long grief can linger, how deeply it can permeate. But slowly, I began to cobble together a life for myself, stacking up weeks, months and even years without my baby brother.

Turning 42 marks the fact that I’ve outlived my brother by 21 years—I’ve already lived two of the short lifetimes he had.

Most of the people in my life today never met my brother. My husband, my two children and the vast majority of my friends know Will only from a handful of fading photographs and the small stack of stories I’ve told them.

Even to me, Will seems foggy now. I can no longer imagine what he would look like if he’d lived—would his dense, sandy-colored hair be thinning? Would he have the same indentation as I do when I furrow my eyebrows, the one that no longer entirely disappears, but leaves a faint quotation mark nestled beneath my forehead? Would he be working in the music industry or at a restaurant? Would his experimentation with drugs have just been a phase he would’ve crawled out of, or would he have struggled with addiction for the rest of his life? But no—he is perpetually young, and I have to squint to remember the contours of his face or the cadence of his voice. Meanwhile, I get older. My life stretches on.

The pain of those early years of grief, the brute force of sudden loss, has faded too. I still think of my brother more days than not, but the tears come infrequently.

And yet in watching my two kids—a boy and a girl, almost three years apart—I have a close-up view of exactly what I’ve lost. As I watch my kids pass the moments of their childhood together, a loop that rolls from name calling to cuddling, I learn what it means to be a sibling. It means experiencing childhood side by side, to be, even with their differences, more alike than anyone else on this earth simply by virtue of having the same parents, of sharing so much space and time with each other. From accumulating thousands of shared moments.

At 42, I know that life is made up of moments. My brother’s early death stole away infinite potential moments. And the further away from my brother’s life that I get, the fewer moments I can remember. What I recall now feels less like a flip book of memories and more like my brother’s essence. He was warm and wild, bright and impulsive.

But in this small lifetime that has passed without him, I have learned to live without him.

“Mama, get in the middle and we’ll circle around you,” my four-year-old daughter announces. We are at my parents’ condo for birthday treats.

“Is this what you do at preschool when it’s someone’s birthday?” I ask her.

“Yes. We’re going to sing you a song,” she says, smiling. “Now get in the middle.”

As I walk to the middle of the room, I glance at the picture of my brother and I hanging on the wall, our heads tilted toward each other, just a pinch older than my kids are now.

I stand in the center of my parents’ living room, surrounded by the people I love the most. My mom and dad, my husband, my son and daughter all circle around me. “Happy birthday to you,” they sing, their voices jumbling together. I take it in, this moment of being encircled. I want to stretch it out, to press it into my mind so I remember it always, the faces of my young children, my mom and dad, my husband, their eyes glittering with love.

The song goes by so quickly.

I am 42.

I’m a sister without her brother. He is like a phantom limb. I will miss him for as long as I am here. But in this small lifetime that has passed without him, I have learned to live without him.

I’m a mother, a wife, a daughter, a friend.

Just for this moment, I am full.