I am an only child. And Erick was an only child for the first five years of his life, until his brother was born. In other words, we had absolutely no preparation for what is going on in our house.

Our three girls are 20 and 19 months apart, respectively. Fiona tells me she has no memory of life without Campbell. (Which really makes me wish we hadn’t crammed so much into those first 20 months of her life. Taking a 4-month-old to the aquarium? Can you say “First-time parents?”). I’m willing to guess that, when Campbell’s old enough to express it, she’ll tell me she has no memory of life without Georgia. And Georgia will never, ever know what it’s like to not share a house with two incredibly loud and overly affectionate big sisters.

Campbell turned 2 shortly after we moved to Vermont, and that milestone was also a turning point for the relationship between Fiona and Campbell. It’s hard for me to put into words what this sister relationship is like. Perhaps those of you who are blessed with sisters could do a better job, but perhaps it’s really a nonverbal force. I will say that their relationship gets stronger every day (and louder, and more fraught with fights), that it’s one of the things that makes me happiest about being a parent; Erick and I find ourselves looking over their heads at each other and exchanging “WOW” glances almost daily.

It’s hard to imagine two people better suited to each other than Fiona and Campbell. Fiona is more moody and introspective, but sweetly sensitive to the emotions of others; Campbell lives life all out on the surface, and could care less what others think of her. Look askance at Fiona and she’ll crumble; yell at Campbell and she’ll either ignore you or smile. Fiona has a very active imagination and is scared by even the thought of evil; Campbell will tell you several times a day that she’s “not afraid of anything!” Except that Campbell is really, really afraid of doctors; Fiona loves going to the doctor. When they play princess, Fiona is always the princess, and Campbell is almost always her pet cat (or lion). BUT, they both love chocolate, and ice cream, and peanut butter, and singing, and reading, and running around in circles, and flashlights, and building pillow forts, and animals, etc etc. Here are a few examples to illustrate their relationship:

-Campbell rarely addresses Fiona by her actual name; to her, Fiona is “Sister.” I finally pointed out to Campbell that she does, in fact, have another sister, which might become confusing once Georgia is old enough to respond. Campbell looked at me blankly, and continued playing.

-Due to a combination of their birthdays and the kindergarten cut-off date here, Campbell will be just one year behind Fiona in school. This means that next year they’ll be attending the same preschool, Fiona with the 4-year-olds and Campbell with the 3-year-olds. Fiona can’t wait; she’s already telling Campbell: “Next year you’ll be a big girl and you’ll go to my preschool. You’ll be in the 3-year-old room, but I’ll see you on the playground.” And Campbell can’t wait; she told me, “Next year I’ll protect Sister at naptime and on the playground.” I’m sure she will.

-When Fiona started full-day preschool this year, I thought that Campbell (as the classically overlooked middle child) would relish the chance to have three days a week alone with me. I was wrong. By about 11:00 each preschool day, Campbell and I have some version of this exchange:

C: Mommy, where’s Sister?

Me: She’s at preschool, Cams. We’ll pick her up this afternoon.

C: Let’s go pick her up now!

Me: Why?

C: Because…I love her!

-And finally, the sleeping situation. One of the best parenting decisions we ever made was to have our girls share a room. This was partly necessity: living in the Bay Area on a graduate student’s stipend, we couldn’t afford to rent more than a 2-bedroom house — and partly philosophy: we knew from recent travels in East Africa that our girls were lucky to have beds, let alone a room/we hoped they’d learn the joys of sharing/we hoped they’d become better sleepers as a result.

Well, it’s hard to know whether sharing a room made them good sleepers, but if one sister wakes up screaming in the night, the other two do have an amazing ability to sleep through it. This soundness of sleeping is offset somewhat by the nightly bedtime party that happens after we say goodnight and shut the door; our girls probably get to sleep much later than they would sleeping alone, since they spend upwards of an hour talking, singing, and playing in bed. (For an idea of what this sounds like, imagine Kate Bush, times 3. Imagine these 3 Kate Bushes singing, for the sake of argument, “Wuthering Heights,” but each at a 1 second delay. And there you have it). This has only intensified since Fiona decided that sharing a room wasn’t enough; now she shares a bed with Campbell. So, the scene at bedtime is this: Campbell at the head of her twin bed, Fiona facing her at the foot, and Georgia standing up and peeking over the railing of her crib to see what her crazy sisters are up to. And they love it; they love, love, love it.

This sisterly sleeping arrangement is my biggest carrot and stick. If there’s too much fighting or laughing after bedtime, all I have to do is threaten to move somebody to another room, and everything settles immediately. On the other hand, just about the best reward I can offer them (besides chocolate) is the chance to nap together. I separate the girls for naps, because Fiona doesn’t usually sleep during naptime anymore and Campbell still needs her sleep, but they lobbied so hard to be able to nap together that I’ve started to allow it as a once-a-week “treat.” Nobody sleeps, but they will happily not nap together for hours.

Where Georgia will fit in to all of this, I just don’t know. What I do know is that both of her older sisters adore her, and they want to hug, hold, and carry her until she gets fed up. Georgia adores them back; her huge smile lights up whenever she sees one of her sisters, and she is just chomping at the bit to be able to join in their shenanigans. But the oldest two are so close, it’s almost enough to make us have a fourth child just to give Georgia her own special buddy. Almost.

I know these girls will grow up and fight more, and about more serious things than who gets to hold the Barbie. I know that a day will come when they’ll want their own rooms. I know that they may end up living miles away from each other. But whatever happens, I just hope that they will love each other forever. I hope that Campbell will always be willing to protect Fiona at naptime, and I hope that Fiona will always be willing to hold Campbell’s hand at the doctor’s office. Because I can’t think of a better gift as a parent than to know that your kids will have each other after you’re gone.