I got my first brand new car in my twenties. It was a silver Volkswagen Jetta with a dark grey interior and automatic sunroof. I was in love, freed, finally, from a completely unreliable and unwieldy Pontiac Grand Am that guzzled gas and was impossible to parallel park.

On a Thursday evening, not even a week after I’d gotten the Jetta, my brother called and asked to borrow it for a weekend trip to the Hamptons. Actually, “asked” isn’t quite right, it was more like he told me he was going to borrow it for a weekend trip to the Hamptons. And so he did. He brought it back Sunday night, dropped it off quickly, said thanks and was gone.

I opened the driver’s door the next day, look down, and in the bright sun discovered that my brand new car was full of sand. Of course I was horrified. Sand! In my new car! I called him right away, wailing. How could he? It was my NEW CAR! And he said, as calm as can be, “C’mon, Deeda (my family nickname)! You know my sand is your sand!” This stopped me in my tracks because, alas, it was true.

We’re 13 months apart and have made it though almost everything together, including growing up in a housing project with a drug-addicted father. I was there when he messed up his shoulder and lost his college football scholarship. He was there when I moved into my first apartment, a horrible sixth-floor-walkup cave that he said was great and then later admitted was a hovel but he wanted to be positive so I’d finally get out on my own. Even now, he’s my go-to tech guy and I help him write big reports for work. My brother has never let go of my hand, even when it’s been slippery and hard to hold. I can’t imagine being here without him and love that we’re the only two people on the planet who shared our mother’s womb.

I always knew I’d be a mother and naively assumed I’d have at least two children who would have the same bond I share with my brother. Yet for years I had recurring dreams about a little girl who was always alone. I knew intuitively that she was my daughter, but never understood that she would be my only child.

I met my husband when I was 39. We got married when I was 41 and immediately started trying to have a family, but I had trouble getting pregnant naturally. Eventually, we sought help and got very lucky. After just three months of treatment, I was not only pregnant, I was pregnant with twins. My husband literally whooped in the exam room. I think we’d both been secretly hoping for twins, knowing that we’d gotten a very late start and this might be our only chance at having biological children. It was very early though and our excitement soon turned into disappointment when we learned that one of the fetuses wasn’t viable. I struggled for a long time (and still do) with the horrifically conflicting emotions of being pregnant and miscarrying at the same time. But the rest of my pregnancy was perfect. I delivered a beautiful baby girl and fell headlong in love.

We tried again when she was 10 months, but by then I was 44 and while tests showed I still had plenty of eggs left, they were, as my dear doctor kept reminding me about “old” eggs with “tough shells.” (I kept picturing tiny sperm with pickaxes trying to fight their way in.) And, after months of treatment with no success, we just kind of stopped trying.

I admit I’m having a hard time accepting that my daughter is and will be an only child. I want for her what I have with my brother – a bond she can hopefully rely on for her entire life and a relationship that impacts who she is and how she is in the world. And while I realize there’s no guarantee that siblings will get along, I wish I could provide her with the possibility.

Of course I worry, too, about what will happen when her father and I are old. My mother is 72 and while she’s in very good health, my brother and I talk to her every day and reach out to each other if we’re concerned about her. Most recently, I worry if I can’t reach her. I’ll check with him to see if he’s spoken to her that day, and usually he has. He’ll remind me that she’s playing bridge and turned off her mobile phone. Who will my daughter call if she can’t find me? Who will she complain to when I’m annoying? Who will she giggle with when I make an embarrassing speech at Thanksgiving dinner?

Most of all though, I’m afraid my daughter is going to be lonely. At four, she’s already extremely social and often asks to play with other children. Her father and I try to fill in as playmates, but know it’s not quite the same. Of course I had to have an only child who is also a social butterfly. And selfishly, a sibling would take some of the pressure off me. I love playing with my daughter but at 47, I don’t always have the energy to keep up with her.

In the end, it is what it is. We’ve thought about adoption and we’ll keep thinking about it. We’ll take her on playdates and make sure she spends time with her cousins. She’ll keep basking in the bright light of always being the center of our attention and hopefully not become too spoiled because of it. She’ll learn that independence can be a very good thing that will help her cope in immeasurable ways as she gets older. And most of all, she’ll know that even though we didn’t give her a sibling, we’ll do all we can to give her everything else she needs.