I thought Jack Nicholson had been conceived through an incestuous union, (ie: his mother was also his sister). That's only marginally true.
Jack's mother was young and unmarried, and he was primarily raised by his maternal grandparents. They told him that his mother was his older sister, and he didn't find out the truth until 1974, at which point his mother and grandparents had already died.
Jack's mother was young and unmarried, and he was primarily raised by his maternal grandparents. They told him that his mother was his older sister, and he didn't find out the truth until 1974, at which point his mother and grandparents had already died.