In Sarah's Key by Tatiana de Rosnay, Sarah and Julia are similar in their determination and their love, but they are quite different in how they respond to the events in their lives.
Sarah is just a young girl in the first part of the novel, but she is determined to save her beloved brother, Michel, when the French police come to arrest her family during World War II. Sarah locks Michel in a cupboard, thinking that she will be able to return for him quickly, as soon as her parents sort out the mistake. Sarah, however, does not understand the real situation. She and her family are Jewish, and they are being taken to a concentration camp. By the time Sarah escapes (at great risk to her own life) and returns to Paris to try to save Michel, it is too late. He is dead.
Sarah grows up and marries, but she can never let go of what happened to Michel or of her guilt. She writes letters to her brother, trying to come to terms with the events of her life. Eventually, though, she falls into despair, and her son believes that the car accident that killed her might have been suicide.
Julia is also a person filled with determination and love. She loves her family, especially her daughter Zoe, and she stays with her husband, Bertrand, even though he is rather too demanding and insulting. When Julia learns of Sarah's story, she is determined to find out more about Sarah and her family. She tracks down Sarah's son, William, who at first does not want anything to do with Julia. Her husband's family also encourages her to leave well enough alone, but she will not. Julia wants to know the truth.
When Julia discovers that she is pregnant, her husband demands that she get an abortion. She refuses. She loves this new child. Eventually, Julia leaves Bertrand, and she and her daughters move to New York. Julia names the baby Sarah, after the woman whose story she has worked so hard to discover. Unlike Sarah, though, Julia takes charge of her life and refuses to give in to events and negative emotions.