Almost-Orphans, Crazy Father Figures, and Medieval Castles

I just finished reading A Brief History of Montmaray by Michelle Cooper, a historical novel about young royal cousins on an fictional island nation on the cusp of World War II.  I was immediately struck by its similarities to I Capture the Castle by Dodie Smith, a YA classic that I had missed and recently read on my quest to fill in some of my children's literature gaps.  I wasn't the only one - one of the blurbs in my paperback edition made the connection too.  The similarities are so numerous and specific that I made a list:

• Orphans or de facto orphans who have to largely fend for themselves, check.
• Said almost-orphans live in genteel poverty, check.
  
• Mentally ill father or father figure, check.
• Isolated medieval castle, check.
• 1930s setting, check.
• Teenage narrator who narrates by writing in her journal, check.
• "Plain" narrator and more beautiful older sister/cousin, check.  
• Love interest named Simon, check.

There are, of course, some differences, the major one being that A Brief History of Montmaray addresses politics and the impending world war whereas those go unmentioned in I Capture the Castle.  A Brief History of Montmaray is also the first book in a trilogy. 

Can you think of any other two books with so many similarities?  I wrote about others that came to mind here, particularly Roald Dahl's classic Charlie and the Chocolate Factory and Wendy Mass's recent book, The Candymakers and here.