Still Life with Memories series content ratings

Content ratings for books in the Still Life with Memories series. How content ratings are chosen

• My Own Voice (Still Life with Memories Book 1)
• The White Piano (Still Life with Memories Book 2)
• The Music of Us: WWII love story (Still Life with Memories Book 3)
• Dancing with Air: WWII Love Story (Still Life with Memories Book 4) PG-13