Curly sister slept with her brother, putting her twat under his rigid manstick

So while my parents were away, my curly-haired sister decided to share the bed with her sibling. At first the youngsters were uncomfortable, but then as they began to fondle each other's genitals they separated so much that the sister quickly put her cunt under her standing cock and gave herself to her brother, who fucked her from behind as hard as he could until her sperm spurted out.