Book Where The Child Has To Hide In The Attic

Best known for books like flowers in the attic the wildly over the top 1979 gothic family saga about four children locked in an attic by their grandmother vc andrews died in 1986 but that.
Book where the child has to hide in the attic. They live with their happy mother and happy father in their happy little house and are overall quite happy together. I finally started a search for the name of the book where a little girl found magic in the attic. And the human child follows the ghost child up the stairs of the house and whatever attic is up there turns into a beautiful house looking beautiful and in good. I will likely get to these impostor books one day but not today.
He meets a girl and they become friends. As a result corrine collaborates with her formidable mother to hide the children in the north wing of the mansion where they will be unnoticed by the servants and have access to the attic. But throughout the book there are flashback sequences where the ghost child wants to show the human child what her life was like and says follow me in an excited playful mood. A shadow child is the 3rd kid.
The people are only allowed to have 2 children so anything after 2 they hide them. I am going to buy this book and keep it in my adult collection because out of the hundreds of books i ve read in my life this book is the one i have thought about over the years that made a lasting impression on me as a child. Anyway flowers in the attic the first book is about these four little happy children named chris cathy carrie and corey dollanganger. I have mixed feelings about this book.
In the book you are only allowed to have two children. Luke has 2 brothers named mark and matthew and a mother and father.