It seems you might be thinking of Jem, Atticus's son. While the novel doesn't explicitly state when or how Jem learned to read and write, it's implied that he was taught by his father, Atticus, at an early age.
Here's why we know this:
* Atticus reads to Jem and Scout: Atticus often reads aloud to his children, especially from the book "The Gray Ghost." This suggests he believes in early literacy and encourages his children to read.
* Jem can read by the time he's six: Jem and Scout are both young in the novel, and Jem is shown reading Scout's schoolbooks at age six.
* Scout learns to read later than Jem: This suggests that Jem learned to read before Scout, likely with Atticus's help.
Although the book doesn't explicitly state Jem's learning process, the evidence suggests he was taught by his father.