There was a book I read years ago and I believe the story was even made into a movie in the 80s. A handful of orphan kids run away from the orphanage together. They move into an old house somewhere and start living as a family, trying to hide the fact that there are no parents. The oldest kid, a teenage boy, ghost writes an advice column, pretending to be an older woman.
I'd enjoy reading the book again, but I can't remember the title!