OK how about this one:

During the summer Draco/Ginny goes to stay at their uncles house. (mistlethwait manor!) anyway while there they meet up with Draco/Ginny and then with their cousin no one knows about.

Other than that I've got nothing for a story...

I just thought it was a cute book and movie and would make a good story. I have absolutley no time or any real idea as how to do this so I thought maybe somebody here might!!