Jem is a typical, Southern-bred young man whose father is both his anchor and his subject of admiration. Yet, he learns a whole much more about the depth of character of his father, which brings him closer to Atticus, and makes him want to emulate him more.
Atticus is a great parent to his children: Even at the absence of a mother in the family, he has taken upon himself that the children have a motherly figure in their aunt, and in the servant, Calpurnia. Also, Atticus has taught Jem about the value of humanity, about the importance of humility, and the truly valuable things in life.
In turn, Jem's character (as he grew up in the story) became more and more like his father: Courageous, and strong. Jem was sure to extend Atticus's legacy and be like his father when he becomes an adult.