Oprah Winfrey has revealed her big secret.  On Monday's broadcast of The Oprah Winfrey Show, she announced she has a half sister that she never knew about.  “This, my friends, is the miracle of all miracles” Oprah stated, adding that it’s, “a bombshell family secret that left me speechless.”

On the show -- which was aired live in Chicago where Harpo is based --  Oprah told the story of how she found out about Patricia, her half sister who was born to her mother, Vernita Lee on April 26, 1963  in Milwaukee, Wisconsin.  At that time Oprah was 9 years old and living in Nashville with her father.  Oprah said she never knew her mother was pregnant.  Vernita gave up the child at birth and kept it a secret all these years.

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Oprah Winfrey’s got America buzzing about the surprise reunion she's advertised for her show Monday, and RadarOnline.com has all the details for you.

The Windy City media mogul said in a promo last week: "I was given some news that literally shook me to my core.

"This time, I'm the one being reunited," Oprah, 57, said in the spot. "I was keeping a family secret for months, and on Monday, you're going to hear it straight from me."