"...
Born on April 22, 1937, his mother was all of 17 years
old. Named June Frances Nicholson, she was a showgirl
dancer. Nicholson in turn was raised by his maternal
grandparents, John Nicholson and Ethel May. He only
learned in 1974 after his birth mother was dying of
cancer that he found out who she was, raised to
believe that she was in fact his sister..."
http://www.catholic.org/news/ae/celebrity/story.php?id=52289