Jacob Grimm is one of the central characters in the series, presented as a fairy tale compiler working alongside his younger brother, Wilhelm. The character is depicted as a young man in a historical European setting, engaged in the task of collecting and writing down the stories that would become famous fairy tales. His life is intertwined with his family, particularly his work with Wilhelm and his interactions with his younger sister, Charlotte.

In terms of personality, Jacob is shown to be more observant and contemplative than his brother. He often takes a direct and somewhat serious approach when recounting the details of a story, such as when he describes the harsh living situation of Cinderella without softening the details. This suggests a commitment to the reality of the narratives, even the unpleasant parts. He is not without a sense of humor or playfulness, as seen when he teases Charlotte about her dislike for meat during a family dinner, a moment that shows a lighter, brotherly side to his character.

Jacob's motivations are closely tied to his work and his family. He appears dedicated to the process of understanding and shaping the fairy tales. A significant aspect of his character is his influence on Charlotte. In one instance, when observing her play with dolls, he encourages her to punish a doll representing an older sister who is being mean to her brother, telling her to teach the doll a good lesson. This moment reveals a subtle but notable influence on Charlotte's sense of justice and punishment, suggesting Jacob’s analytical mind is applied not just to stories but to moral lessons as well.

His role in the story is primarily that of a compiler and narrator. He, along with Wilhelm, serves as a framing device, presenting the classic tales to Charlotte. The brothers often discuss the meanings and consequences of the stories. For example, when Charlotte questions why the Pied Piper was not paid for his work, Jacob offers a cynical theory: that the villagers unashamedly broke their promise, which led the Piper to steal their children. This shows Jacob is willing to explore the darker, more logical consequences of human selfishness within the fairy tale framework.

The key relationship in Jacob’s life is with his brother, Wilhelm. They work closely together, with Wilhelm often providing a more optimistic counterpoint to Jacob’s straightforward delivery. Another critical relationship is with his sister, Charlotte. Jacob engages with her directly, answering her questions and observing her play. His interactions with her are formative, as he and Wilhelm are essentially her educators in morality and consequence through the medium of their fairy tales.

Throughout the episodes, Jacob does not undergo a dramatic personal transformation but is consistently portrayed as a thoughtful and sometimes stern figure. His development is more about the deepening of his interpretations of the tales as he discusses them with his family. There is a notable moment where he is seen staring out a window, fixated on Charlotte playing, indicating a protective or deeply observant nature regarding her development.

Jacob does not possess any supernatural or physical abilities. His notable abilities are intellectual: he is a skilled storyteller, an analyst of human nature, and a diligent worker dedicated to his craft. His power lies in his ability to see the cause-and-effect within the moral landscapes of the stories he collects.