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