In Miss Peregrine's Home for Peculiar Children, how does Jacob grow from the relationships he experiences?

In the novel Miss Peregrine's Home for Peculiar Children, Jacob begins as a young child who is obsessed with his grandfather's stories before going through adolescence and becoming jaded. As a young teen, he is much more suspicious and doubtful but chooses to listen to his grandfather's dying message and look for the clues he left.
Jacob meets many interesting characters and develops strong relationships with other children, including Emma and Millard. Through his experiences, he goes from an isolated, lonely, and jaded child to a much more engaged and active individual. He takes more action and pursues solutions at the end of the novel and is much more connected with his friends, whereas he started the story as something of a loner.