“I love you Mummy” he says, pressing his flushed cheek to my enormous belly.  “And I love baby brother, too”.  My sweet son kisses my belly, his (almost) four-year-old frame wrapped around my leg.  I bend slowly to lift him up, settle him on top of where his baby brother is kicking furiously at my ribs, and he puts his head on my shoulder.  “SEE Mummy!  You CAN lift me up!” he whispers, and my heart breaks open into a million tiny pieces.

They say that your love grows deeper.  That your heart expands.  That there will always be room in your arms for more children, room at your table for more plastic firetruck dinner plates.  The mothers who have walked this road before me tell me that new babies find more curves of your body to snuggle into, everyone fitting perfectly, nestled together like a set of measuring spoons that were always meant to accompany each other.

So I suppose that it must be true.  But what if it isn’t?

Our baby, the baby that we have longed for, the baby that I prayed for every month when the screen on the pregnancy test glared back at me with a blank stare….that baby is due to arrive in our arms in just five short weeks.  I know that he is meant to be my son, this sweet boy who wiggles and kicks inside of me, letting us know that he is excited to join the world and our adventures.  I reach for him every morning, willing him to make himself known as I lie half awake in bed, praying that he is still with us.  I rest my hand on my belly every night, feeling him stretch and move, while I listen to his big brother take soft breaths over the baby monitor.  One hand on our future, one ear listening to our present.

Baby Ben, we know that you will complete our family when you arrive.  I dream of watching you toddle after your brother on the playground.  I can already see how you will sit knee to knee in the bath tub together, both splashing water over the side and onto the floor while I pretend to be frustrated with you.  Max is already putting his stuffed friends to bed in your crib.  Groundhog, Doggie, and Bunny have been napping where you will rest your head.  You have your very own sleeper suits and new blankies, and many pairs of cool shoes so that you can match your Daddy and your brother.  Max has decided that you like the “Baby Bumblebee” song, and we sing it to you as you lie curled tightly in my belly.  “Mommy, does baby have any toys to play with in there?” he asks.  “Is it really dark?  What does he eat?”  I know that you hear our voices at storytime each night, quietly participating in the peaceful ritual of reading the train book and singing the night-night song, even though you haven’t arrived yet.  You are creating a space for yourself, and we are slowly making room.

Perhaps my heart is practicing it’s stretching already.  When I gently move Max off of my aching belly and nestle him in the crook of my arm instead, I am learning to love you both.  When I tell Max that I will be able to play blocks with him just as soon as I’ve finished my lunch, I am learning to care for you both.  When I dream of what it might feel like as you slip from my body, or drink from a breast that will hopefully fill with milk, or soothe the squeaky cries that are uniquely your own, I am learning to value the stories of both of my boys, different as they might be.

Max and I have grown up together.  He made me a mother, and taught me how to parent.  When I look at his huge hazel eyes, I see every dream that we have shared, reflected back at me.  His little hands fit perfectly in mine.  I have memorized the soft whirl of hair that tickles the back of his neck, and how it feels underneath my fingers.  I understand him, I interpret him, I know him with every fiber of my being.  I am terrified of how his world will change.  Will he know that he is still “my best”?  Will he know that he can still count on me to be the first hug every morning, and the last kiss every night?  Will he still want to dance with me as the music rings out in the living room, to a favorite song that we both know every word to?  How will I explain to him that my love will only grow?  That one day, when he puts on a Halloween costume he’ll have a built-in trick or treat buddy to walk up to every door with.  That he will have a partner in crime on family vacations, someone to watch for him at the window when the school bus pulls up, a co-engineer of lego castles, and a best man at his wedding.  Will the two of you feel secure in how special you are, knowing that you are not only a gift to your parents, but a gift to each other?

It’s when I think of the dreams that our family has yet to fulfill, that I am soothed by the fact that we will be ok.  My heart will expand because there are so many good things to fill it with.  So many new ways to love, that are waiting to be discovered.  Right now I can only imagine the day when our sweet baby boy makes his entrance into this world.  But if loving Max has taught me anything, I can be sure that my heart will explode as I look into Ben’s eyes for the very first time.  This time, I will see not only Daddy in the eyes of my newborn son, but my sweet “big boy” as well.  Our lives, our dreams, the hope that we have for the years to come, all reflected back in the pure spirit of a tiny human who is navigating his first few hours of life.

And until then?  Until then, I will take my first son’s hand and twirl him around to the music just a few minutes longer.  I will read one more story every night, just to feel the warmth of Max’s small body against mine.  I will inhale the time between, and keep these moments sacred so that Max will always know that I remember.  I’ll remember when he was my smallest.  I’ll remember when he was my only.

Two boys.  One mama’s heart.  One love.  Goodnight my sweet sons.  Sweet dreams to you both, the one that has already stolen my heart, and the one who is growing underneath it as it expands.  I have loved you both since before I even knew you, and that love can only grow stronger, in the time between.

Photos by Richelle Wetzel of Lissymack Photography

This post originally appeared at The Huffington Post. Kim blogs at Mama By The Bay, which began as a love letter to her son Max.