Dear Z,
You're going to be a big sister soon. You know that, at least on some level. But do you know how much your baby sister is going to rock your world? I know you'll love hugging and kissing her, helping with the baths and the diapers and examining all her tiny little features. You'll want to show her off to your friends and ride together in our new double stroller.
What you won't want to do is share Mommy. I see the green flash in your eyes when I've got another child in my arms or on my lap. You've started pretending to be a baby and you even asked yesterday, "Is it okay if I say I don't want a baby sister?"
You're going to get extra special Daddy time (over and above what he already dedicates to you), and I fear you're not going to relish it. Instead, I worry my heart will be wrenched in two. I'll have your younger sister attached to the boob while you scream "Mommy do it!" as Daddy or Nanny run the bath/cut your food/take you to the park.
But you'll adjust, and it will ultimately be good for you. Having a sibling is a lifelong exercise in learning to share. Take it one big sister to another: your little sister will steal Mommy's attention. She'll steal your toys. Your diary. And your friends. Sometimes she'll be your worst enemy. But more often she'll be your best friend. Your built-in playmate. Someone who admires you (but will never admit it).
So remember to think of all that stealing as sharing. Because chances are you'll be sharing your lives together long after your parents leave the picture.