Ranma and Akane: A Love Story might count, depending on your definition of "child". Ranma shows up in Nerima (not the usual beginning) and will go to Furinkan. So sie tosses a coin to decide what sex sie'll be when sie does. This bespeaks a long-enough familiarity with the curse that sex is a matter of tossing a coin.
This is one of my favorite stories. It's long, and in an unusual format, but it is a wonderful AU. It's not finished, but the first story arc is. You'll recognize that end when you meet it.