It’s been building up for about a week now and Oprah has finally revealed her “big secret” on an episode of her show.

Oprah celebrates her 57th birthday this Saturday and in case you were wondering what it is that “literally shook Oprah to her core”….

Video: Oprah Reveals her BIG SECRET…

Oprah Winfrey recently learned she has a half-sister ? a Milwaukee woman who was put up for adoption by Winfrey’s mother nearly 50 years ago.

Winfrey announced on ?The Oprah Winfrey Show? that aired on Monday that a Milwaukee woman named Patricia discovered that the two were half-sisters.

The woman says she had been searching for years for the identity of the mother who gave her up for adoption in 1963. She says she learned in 2007 that Winfrey was her half-sister. On her program, Winfrey says she learned about Patricia last November.

Winfrey says she was 9 years old and living with her father when her mother had the daughter and gave her up for adoption. She says she never even knew her mother was pregnant.

VIDEO: Oprah Half Sister Episode (Part 1)

VIDEO ~ Oprah Half Sister (Part 2)

Winfrey says the two met on Thanksgiving day and she openly thanked her sister for keeping the secret until she felt the need to reveal it.

“She never once thought to sell the story,” Winfrey said, describing how she felt betrayed by other relatives who sought publicity or money.

Patricia said she didn’t consider revealing that she and Winfrey were half-sisters to anyone but Winfrey, explaining that she did not want to hurt Winfrey.

“Family business should be handled by family,” Patricia said. “It couldn’t be handled by anyone else. That’s not fair. It wouldn’t be fair to you.”? READ MORE