Oprah Winfrey on Monday revealed that she had a half-sister that she only found out about late last year, saying the news left her speechless.

Welcoming single mother of two Patricia to an emotional reunion on her daytime talk show, Winfrey said her mother Vernita Lee kept the birth in 1963 a secret and gave the baby up for adoption.

Winfrey, 56, said she was only nine years old and living with her father when her mother became pregnant.

"Imagine my shock just a few months ago, at the end of October, when I found out I have another sister living just 90 minutes away," Winfrey said.

"For the most part my life has been an open book and on the show I think I've seen about everything. And I thought nothing could surprise me anymore, but let me tell you I was wrong," she told viewers.

Patricia, whose last name was not revealed, said she had been raised in foster homes since age 7.

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.

"She (Patricia) never once thought to go to the press. She never even thought to sell her story," Winfrey said.

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. She became pregnant at the age of 14 but her son died shortly after birth.

But Winfrey went on to become the most influential woman on U.S. television, hosting a talk show that is in its 25th year, and launching her own television network on January 1.

Patricia, who now lives in Milwaukee, and Winfrey met the first time at Thanksgiving last November, they said.

Asked by Winfrey why she had given Patricia up for adoption and kept the baby a secret for so long, Vernita Lee said that she had felt unable to take care of her.

"I thought it was a terrible thing for me to do," Lee said.