strikes the Island, and the Captain's house is destroyed.  He stays with the Bradshaws for a few days.  Sara Louise falls in love with him.

- The Captain moves into Trudy's house and marries her when she gets out of the hospital.  Trudy dies a short time later.

- The Captain uses Trudy's money to send Caroline to school in Baltimore.  Sara Louise is devastated that once again she has been overlooked.

- Caroline leaves for school.  Call leaves for the navy.  Sara Louise is surprised to notice Call has grown up.  She hopes when he returns, they might start a relationship.

- Call returns a grown man and announces his engagement to Caroline.

- The Captain is invited to the Bradshaws for Christmas dinner.  He tells Sara Louise that she was never meant to stay on the Island.  He challenges her to make her own dreams come true.

- After talking with her mother, Sara Louise realizes that the only thing holding her on the Island is her own fear.  She is gratified and finally at peace when her mother tells her that when she leaves, the family will miss her more than they miss Caroline.  Her mother's words make Sara Louise see that even though she has always lived in her sister's shadow, she is and has been deeply loved and valued.

- Sara Louise attends the University of Maryland on a scholarship.  She becomes a doctor and goes to work in Appalachia.

- Sara Louise meets Joseph Wojtkiewicz and marries him.  The two have a son whom she names Truitt, after her own father.

The book is called Jacob Have I Loved as an allusion to a Bible verse. An allusion is a reference to a historical event, work of fiction, art piece, etc. from another work. Romans 9:13 says,

Just as it is written: "Jacob I loved, but Esau I hated."

This verse is an allusion to the biblical story from Genesis 25-27. These sections chronicle the struggle between Jacob and Esau, two brothers who fought over their inheritance. Culturally, the inheritance and blessing were intended for the older brother, Esau, but after a string of events, the younger brother, Jacob, ends up with the inheritance and blessing. This was predicted in Genesis 25:19-34 when the boys' mother, Rebekah, was pregnant with them.

The Lord said to [Rebekah],

“Two nations are in your womb,
and two peoples from within you will be separated;
one people will be stronger than the other,
and the older will serve the younger.”

You are referring to the book by Katherine Paterson. The book broadly speaking is about the sibling rivalry between Sara and Caroline. Caroline is by far the more popular of the two. She is prettier, more talented, and so gains attention. The book is about how Sara frees herself from this complex and finds freedom and peace. 

The title of the book might sound odd, but it actually comes from one of the most famous sibling rivalries in the history of the world. It comes from the Old Testament. In the book of Genesis, we read of Isaac, one of the patriarchs. He has two sons (twins), Esau and Jacob. In this story, Isaac loved Jacob more than Esau; hence, the rivalry started. 

The apostle Paul in the New Testament stated: "Jacob I have loved, be Esau I have hated" in Romans 9:13. Here Paul is referring to a different rivalry, but similar dynamics are in place. 

In conclusion, the book by Katherine Paterson uses the rivalry in the Bible as the backdrop to her story. 

In some ways, the fact that Wheeze's two closest friends leave the island start the chain of events that lead to the climax of the novel.  Louise has struggled her entire life to figure out what the real meaning of love is.  She has felt jealousy and a sense of a loss of love because her sister always appeared to get more attention from her parents.  She felt like she made a mistake when she had a crush on the Captain and then he married an older woman to take care of her.  Then Caroline, her best friend, and Call, the boy she has fallen in love with, eventually form a relationship and get married after having left the island.

All of this leads up to Louise's experience in the small town of Truitt where she finds a husband, and upon delivering the two boys and managing to save the one that didn't appear like it was going to make it, she has finally discovered all the various facets and meanings of love.

Jacob Have I Loved centers around Louise and her relationship with her twin sister, Caroline.  Caroline was born sickly and gets more attention than Louise.  Caroline takes voice lessons on the mainland and often gets out of doing chores.  She belittles Louise, though sometimes unintentionally.  She is admired around the island of Rass for her beauty and talent.  Louise is often overlooked.

As Louise gets older, she starts to resent Caroline more and more.  She reflects on a change that occurs inside her when she is thirteen:

I was proud of my sister, but that year, something began to rankle beneath the pride.  Life begins to turn upside down at thirteen.  I know that now.  But at the time I thought the blame for my unhappiness must be fixed—on Caroline, on my grandmother, on my mother, even on myself. (Chapter 2)

As Louise struggles with resentment toward her sister, the Japanese attack Pearl Harbor and the United States enters the war.  Louise faces more adult problems and concerns.  A strange man arrives on the island and Louise is suspicious that he is a spy.  She is wrong and she befriends the man, who she calls the Captain.  She spends time with the Captain and her friend, Call.

Call goes off to fight in World War II.  Caroline leaves for music school.  Louise feels alone on the island.  She decides to leave and attend college herself.  She becomes a midwife.

Sara Louise Bradshaw lives in the shadow of her younger twin Caroline on the remote island of Rass on the Chesapeake Bay.  Caroline is everything Sara Louise is not - "so sure, so present, so easy, so light and gold".  Born the weaker child, Caroline has been the center of everyone's attention from the day she was born, and Sara Louise, not being as obviously needy, has been pushed to the side all her life, and is resentful and bitter.  She resolves to save up her pennies so that she can go away to school on the mainland and escape the confines of her family and the island.

Sara Louise befriends Captain Hiram Wallace, an old seaman with a checkered past who has returned to the island after a long absence.  When a hurricane strikes, the Captain's home is destroyed, and he comes to live with the Bradshaws for awhile before marrying an ailing island woman.  When he comes into a sum of money at her death, he returns to the Bradshaws with the announcement that he has decided to use his windfall to provide an opportunity at boarding school - for Caroline.

Katherine Paterson has created a multi-dimensional character and an absorbing tale in Sara Louise's quest to come to terms with the betrayals in her life and the reality of her self-absorbed sister's presence as she struggles to find her own identity.