Oprah Winfrey on Monday revealed that a Milwaukee woman named Patricia was the half-sister Oprah never knew about until November.

"Yes, it is true," Winfrey told the audience of her daytime talk program, "The Oprah Winfrey Show."

"It is true that my mother, my mother Vernita is also Patricia's birth mother. That means Patricia is my half sister who I never knew existed," Winfrey said.

Patricia, whose last name was not revealed, appeared on Winfrey's show and said she had been raised in foster homes since age 7.

Oprah's mom, Vernita Lee, had given Patricia up for adoption because she thought it would be impossible to get off welfare if she had another child, she said.

Winfrey, 56, said she had no idea she had a half-sister because at the time Lee was pregnant, she was only nine years old and living with her father.

Patricia said she first learned she was Winfrey's half sister in 2007, but kept it a secret because she knew it would create a media frenzy.

Winfrey's personal life has been well documented. She was born in Mississippi to unmarried parents and raised by her grandmother early in her childhood. During her teen years she was shuttled between parents, and was the victim of abuse.

But Winfrey was able to rise above her difficulties, get an education and launch a career in broadcasting.

As a young woman, she moved to Chicago to work in TV news and eventually hosted her own TV talk show. She is now considered the most powerful women in U.S. media with co-ownership of newly-launched TV network, OWN.