The quote "Jem was a born hero" is found in chapter four when Jem, Dill, and Scout are playing out the story of Boo Radley's life. Since Jem is the oldest, he tends to take control of everything that the children play and how they play it. Therefore Jem is the one who divvies out the parts to the other kids, which Scout begrudgingly accepts.

"I was Mrs. Radley, and all I had to do was come out and sweep the porch. Dill was old Mr. Radley: he walked up and down the sidewalk and coughed when Jem spoke to him. Jem, naturally was Boo: he went under the front steps and shrieked and howled from time to time" (39).

Since Scout is the only girl, then, she has to play Mrs. Radley and ends up with little to do but sweep and scream. Dill, on the other hand, "was a villain's villain" (39) and gets to play Mr. Radley. Therefore Jem gets to play the hero in all of their games, so his assigned role is Boo.

The irony of all this is that Boo is considered the hero and not the villain. With all of the superstitious talk about Boo, and the gossip and the fear of him around town, it would seem logical that Boo is the villain of the story. Mr. Radley should be considered the victim because he gets attacked by Boo with scissors, but in the children's story, Mr. Radley is the villain because he locks Boo away from the world. As a result, Jem, being a born hero, must play the hero; so, Boo becomes the unlikely and ironic hero of the story.