Although he identified himself as non-religious, Nicholson was a Reichian: a devout follower of Wilhelm Reich.
Nicholson had reportedly undergone Reichian therapy and he frequently quoted and promoted Reichian teachings.
Although Furcillo-Rose was already married to another woman, he married June as well. Nicholson has claimed that he is not at all religious and that the only times he prays is during jogging.
Jack Nicholson's biological mother was June Nicholson, although throughout his childhood he thought that she was his older sister. The man who was apparently Jack Nicholson's biological father was a Catholic polygamist (or bigamist).
When June discovered she was pregnant (with the baby that would become the actor Jack Nicholson), she informed her boyfriend, a fellow member of her Catholic parish named Don Furcillo-Rose, that he was the father.
Nicholson went on to distinguish himself as a consummate character actor, easily identifiable, yet impossible to easily label or categorize.
Jack Nicholson's adoptive mother (who was actually his grandmother, but was the woman who raised him) came from a devout Dutch Methodist home.
Her family strongly disapproved of her courtship with a Catholic, and she eloped to marry him.