That's the big secret.
"Patricia is my half-sister who I never knew existed," Oprah said on Monday's show.
USA TODAY's Judy Keen reports from Chicago that Patricia - whose last name was not revealed - was given up by Oprah's mom because wanted to get off welfare and knew that if she had another child, that might be impossible. Lee said she "wasn't able to take care of" her new daughter.
Patricia lived in foster homes until she was 7, including some that were "not so good," she said Monday. Patricia said she always hoped her birth mother would return for her.
By 17, Patricia was a single mother. She has two grown children, a daughter and son.
"Oh my God, I have a family" was her reaction when she found out she had three siblings, Patricia said. One of those siblings, the only one still alive, was Winfrey.
Just before Thanksgiving, Winfrey said, she was told "a bombshell family secret." The story would have become public and been "exploited" eventually, Winfrey said, "so I wanted you to hear it from me first."
Patricia is several inches shorter than Winfrey, but the half-sisters are similar in appearance, with round faces and the same smile.
Winfrey said she had no idea her mother had given up a baby when she was 9 and living with her father Vernon Winfrey in Nashville.
Winfrey said in previews for the show that the news "literally shook me to my core" and called the reunion "a miracle."
How did the reunion happen? Patricia said she saw Lee in a TV interview discussing her three acknowledged children and began to put the pieces together. Her son, Andre, went online and found the birthdates of Patricia's siblings, including Winfrey. "We realized that Oprah could be my sister," Patricia said. That was in 2007. Lee and Patricia both still live in Milwaukee.
Patricia kept her connection to Winfrey a secret because she worried it would create a media frenzy. "I did not want her hurt," Patricia said.
Winfrey called their first encounter "a beloved moment."
She then brought Patricia on stage. Winfrey teared up as soon as she was seated beside her half-sister and clasped her hand.
Last week, Winfrey and Patricia visited their mother in Milwaukee. Winfrey said her mother recently had a small stroke.
In a taped segment, Lee said she was "so shocked" to know that Patricia had been trying to reach her. "I thought it was a terrible thing for me to do, that I had done – gave up my daughter when she was born," Lee said.
Lee said she tried to find her baby soon after Patricia's birth and was told "she had left."
Asked how that made her feel, Patricia wept and said, "I always had a feeling that she didn't need to give me up, and her saying that she came back to get me, it means a lot."
Winfrey said her mother "is still stuck in 1963" and still carries "the shame" of Patricia's birth, making her reluctant to welcome her daughter into her life now.
"You can let the shame go," Winfrey said to the camera, addressing her mother. "You can let that go."