Nathan Radley is a gentleman, the brother to Arthur “Boo” Radley. Jem said he “bought cotton,” meaning he did nothing for a living, he lived off the family money and had no job. Nathan is stern and silent with the Radley children most of the time. He is a threatening figure, known to have a gun and shoot in a seemingly indiscriminate way at prowlers that may seem to be in the yard.
The children fear Nathan at first because they fear the house, and the monster that’s supposedly inside it. As time goes on, they begin to empathize with Boo and care about him, and feel that Nathan is keeping him isolated. This situation is clear in their one telling conversation with Nathan Radley over the hole in the tree. Scout and Jem have been finding presents left in the tree, and they start to realize they are from Boo. They are Boo’s connection to the outside world. They realize they are his friends.
Then one day they find cement in the hole in the tree on the Radley property where the presents have been left, and they are stunned. They drum up the courage to ask Nathan if he filled the hole with cement.
"Yes," he said. "I filled it up."
"Why'd you do it, sir?"
"Tree's dying. You plug 'em with cement when they're sick. You ought to know that, Jem." (Ch. 7)
Although the conversation seems innocent enough, the children aren’t convinced. They believe that Nathan filled the hole with cement to keep Boo from leaving the children gifts. They consider it a cruel thing to do, and are sad for Boo. His connection to the outside world is lost.
Nathan does show a softer side when Alexandra comes to stay with the Finches. When all of the neighbors come to greet her, “Mr. Nathan Radley went so far as to come up in the front yard and say he was glad to see her” (Ch. 13). Other than that, he never says much or interacts with the kids much other than to shoot “at every shadow he sees” and walk to and from town.
The children do not have a positive relationship with Nathan Radley, and to them he represents Boo’s captor more than his brother. Since we know very little about him or Boo, we do not know what really goes on in their relationship. We do know that Boo is terribly shy, and he might just have been protecting his brother. After all, Boo interacting with two neighborhood kids might not have been the best idea, and Nathan might have just been looking out for him. All we have is Scout’s perspective, and we never get the full story from Nathan’s.