An article by Thomas in Truth Revolt, notes that in her book, Dunham describes experimenting sexually with her younger sister Grace, whom she says she attempted to persuade to kiss her using “anything a sexual predator might do.” The article highlights book passages where Dunham bribes her sister to kiss her for prolonged periods using what she says “anything a sexual predator might do”, masturbates while she is in the bed beside her, and plays with her one-year-old sister’s vagina (p. 158-9):
One day, as I sat in our driveway in Long Island playing with blocks and buckets, my curiosity got the best of me. Grace was sitting up, babbling and smiling, and I leaned down between her legs and carefully spread open her vagina. She didn’t resist and when I saw what was inside I shrieked. My mother came running. “Mama, Mama! Grace has something in there!”
My mother didn’t bother asking why I had opened Grace’s vagina. This was within the spectrum of things I did. She just got on her knees and looked for herself. It quickly became apparent that Grace had stuffed six or seven pebbles in there. My mother removed them patiently while Grace cackled, thrilled that her prank had been a success.