Harper Lee said this quote

“ Our mother died when I was two, so I never felt her absence. She was a Graham from Montgomery; Atticus met her when he was first elected to the state legislature. He was middle-aged then, she was fifteen years his junior. Jem was the product of their first year of marriage; four years later I was born, and two years later our mother died from a sudden heart attack. They said it ran in her family. I did not miss her, but I think Jem did. He remembered her clearly, and sometimes in the middle of a game he would sigh at length, then go off and play by himself behind the car-house. When he was like that, I knew better than to bother him. ”