Even Oprah has personal life changing moments.

Lara Salahi - ABC News

For years, Oprah Winfrey has promised her viewers shocking reveals on almost every episode of her show. But none was as extraordinary, especially to Winfrey herself, as finding out she has a half-sister.

The surprise was so great to Winfrey, who met her half-sister Patricia on Thanksgiving in 2010, that she said it "shook me to my core."

But while the public announcement and meeting of the two on her show Monday seemed like a joyous union, some experts said it may be because Oprah has had a few months to warm up to her new reality.

"It's a dramatic change in a person's life," said Dr. Howard Belkin, a psychiatrist affiliated with William Beaumont Hospital in Royal Oak, Mich. "That shock and disbelief comes in and you can't conceptualize it at first."

Not all who are faced with family secrets accept the news right away, if ever, according to some family psychiatrists.

In fact, despite three attempts by Patricia to contact her birth mother and Winfrey's mother, Vernita Lee, Lee refused to meet Patricia.

According to Belkin, the range of emotions following the announcement depends on the person's stage in life. Often, the older a person gets, the harder it becomes to accept a family secret, he said.

"[Winfrey] may have this regret of more than 40 years of never sharing her successes with [Patricia]," said Belkin.

via Family Secrets: The Emotions Behind Oprah Winfrey's Revelation - ABC News.