Atticus's sister, Alexandra, has a preoccupation with heredity, and she is particularly proud of her Finch ancestors and how they come from a history of "gentle breeding." Atticus doesn't really buy any of this, however. Although Alexandra revels in the memory of her cousin, Joshua S. St. Clair--who wrote a short volume of "meditatitons"--Atticus has already told the children the truth about him: Joshua had gone
"round the bend at the University... (and) tried to shoot the president... he wasn't anything but a sewer inspector. Atticus said he cost the family five hundred dollars to get him out of that one--"
Alexandra's response was "We'll see about this," and she proceeded to harangue Atticus about his version of her family hero. When he tried to explain Alexandra's views on "gentle breeding" to his children, and how Jem and Scout would have to start to "behave accordingly," Scout soon became bored, and Atticus yelled at her. Stunned by her father's "curtness," Scout was soon in tears. When Atticus saw how Alexandra's edict was affecting his children, he told Scout
"I don't want you to remember it. Forget it."
Since Atticus prides himself on treating all people equally, it is not surprising that his sister's elitist views about "Fine Folks" and family heritage contradicts his own viewpoint. Atticus tends to judge a person for what he is, not by who his ancestors were.