The primary internal conflict in Jacob, Have I Loved was the jealousy Sara Louise felt toward Caroline, her twin sister. Sara Louise felt guilty about her negative feelings towards her sister, but she still let them fester inside of her.
Sara Louise showed her jealousy over Caroline's getting more attention than her. Caroline had been born sickly, and required most of their mother's attention. She had continued to receive attention as she grew older. She was talented and more beautiful than Sara Louise. Sara Louise considered the few minutes after her own birth, before Caroline was born:
They represented the only time in my life when I was the center of everyone's attention. From the moment Caroline was born, she snatched it all for herself (Chapter 2).
When both sisters got sick, Caroline was often rushed to the hospital. Caroline and their mother spent a great deal of time together, whether it was traveling to voice lessons or going to the hospital. Sara Louise never caused her parents to worry. She wished that she had so they had been required to pay her more attention. Growing up, Sara Louise had felt sad and insecure. When she was thirteen, she described an internal change:
I was proud of my sister, but that year, something began to rankle beneath the pride (Chapter 2).
Jealousy and bitterness toward Caroline became more evident in her life. When Caroline sang well during the Christmas concert, Sara Louise was filled with anger. She had dreams of Caroline dying in various ways. When Caroline made little jabs at her, Sara Louise flew into a rage.
Sara Louise struggled with feelings of envy in general. When Call dropped out of school to work with her father on his boat, Louise was jealous of him.