Oprah Winfrey revealed on her television show Monday morning that she has a half-sister she knew nothing about.

The sister, Patricia, had been kept a secret by Oprah's mother who put her up for adoption at birth.

"For the most part my life has been an open book," Oprah said. "I thought nothing could surprise me but I was wrong."

Winfrey said she chose to make the announcement herself so the media would not exploit it. Her sister, Patricia, spoke about being put up for adoption at birth, spent time in foster care and longed to be reunited with her foster mother.

By 17 she was a single mother, Patricia said, and six years later she had another child. When she was 20, she sought out information about her birth mother and then let it go until years later, Patricia said.

The agency contacted Patricia in 2007 with the news that her birth mother did not want to meet her on the same day she saw a local news story that had an interview with Oprah's mother which gave her information that matched up with what Patricia knew about her birth family.

"We realized that Oprah could be my sister," Patricia said.

Winfrey told her audience that it was true that Patricia was her sister. Patricia said she kept her family connection a secret after unsuccessfully trying to reach Oprah's mother, Vernita Lee.

Patricia tracked down Winfrey's niece who is the daughter of Oprah's other half-sister. The pair did a DNA test and it was revealed that they were indeed aunt and niece. That started the ball rolling with family members reaching out to Winfrey who eventually confirmed with her mother that the story was true.

Winfrey shared with the audience home video of her first meeting with her sister this past Thanksgiving Day when Winfrey and her partner Stedman Graham drove to Milwaukee to finally meet her sister.

Winfrey broke down a bit when expressing why she admires her half-sister so much. The talk show host said she has had so many people betray her since she became a celebrity and she was moved by the fact that Patricia kept the story secret.

"She never once thought to go to the press," Winfrey said. "She never once thought to sell this story."

Ironically, Winfrey also had another half-sister named Patricia who died in 2003. That sister was unable to overcome drug abuse and her resemblance to her new half-sister was noted often. Winfrey said she had placed that sister twice into rehab.

"For me, you are Pat on her very best day,” Winfrey said to her new half-sister. “You are who she wanted to be without the drugs.”

The pair sat down with their mother, Vernita Lee, and Oprah asked about her feelings learning about and being reunited with Patricia.

"I was so shocked to know that she was trying to get in touch with me," Lee said. "When I first heard about her, I wasn't afraid but I was a little leery."

Winfrey said she had an epiphany after leaving the meeting at her mother's house: that Lee has been unable to fully embrace her new daughter because she is still carrying the shame of what she had done.

"I would like to say to our mother, you can let that shame go," Winfrey said. "You can let that go."

Winfrey also said that she had a realization about her deceased sister Pat who had sold the story of Winfrey's out-of-wedlock pregnancy to the tabloids which caused a rift between them.

Winfrey said meeting her new half-sister helped her realize that her other sister going to the tabloids was actually beneficial.

"For the first time, I realized that was a gift to me," Winfrey said. "It was gift because it released me from my shame."

Winfrey asked Patricia what has been the most rewarding part of the journey for her.

"Getting my family," she said.