After teasing a "shocking family secret" on her show last week, Oprah Winfrey yesterday revealed that she'd recently learned she has a half-sister named Patricia. The two met for the first time last Thanksgiving, and Oprah introduced her to fans on Monday's show. (See Oprah meet her half-sister for the first time.) Here, a brief guide to what's known about this new figure in Winfrey's life:

Who is Oprah's half-sister?
While her last name has not been made public, Patricia was born in Milwaukee, Wis., in 1963. Oprah's mother, Vernita, put the child up for adoption, and Patricia spent the first seven years of her life in various foster homes before being permanently adopted. "I made the decision to give her up because I wasn't able to take care of her," Vernita says. Patricia is currently a single mother with two children of her own named Aquarius and Andre.

How did Oprah not know about Patricia until now?
When her mother gave birth to Patricia, the 9-year-old Oprah was living with her father in Nashville, Tenn. I "didn't even know my mother was pregnant," says Oprah. "So imagine my shock just a few months ago."

Why did Oprah delay the announcement until January?
Cynics say she timed the revelation to coincide with the launch of her new TV network, OWN. "Clearly," says Fox News' Dan Gainor, "Oprah had plenty of time to envision how she wanted to handle the family news and she just as clearly used it to promote the family business."

How did Patricia discover she was related to Oprah?
When she was 20, Patricia made her first attempt to contact her birth mother, but didn't follow up. In 2007, at the urging of her own children, she tried again. The state gave Patricia birth records revealing that she had three siblings, but informed her that her mother had no wish to meet up. That same day, Patricia saw an interview with Oprah's mother on television, and learned that details about Oprah's siblings matched the information on her birth records.

How did Patricia contact Oprah?
Given Vernita's refusal to meet, Patricia reached out to Oprah's niece, Alisha, who was immediately struck by the family resemblance. "[There was] just something about her," Alisha says. "It just felt right." A DNA test confirmed their kinship. Months later, Alisha emailed her Aunt Oprah about their new family member.

Did Patricia try to contact Oprah through the media
No, although she did try to reach out to Oprah through her pastor. "She never once thought to go to the press,"  Oprah says. That meant a lot to Oprah, says the media mogul's best friend, Gayle King, as quoted by ABC News: "As you know [Oprah] has been sold out on many occasions by friends, by co-workers, in some cases family, with stories that weren't as legitimate as this." As Jessica Wakeman at The Frisky notes, It remains to be seen "whether Patricia is classy, or deathly afraid of her powerful new half-sister."

When did the half-sisters first meet?
On Thanksgiving Day, Oprah and her partner Stedman Graham drove to Milwaukee to meet Patricia. On seeing her, Oprah noted her resemblance to her other sister, coincidentally also named Pat, who died in 2003 after a prolonged struggle with drugs. "It was so uncanny to us and to everybody in this family how much this Patricia looked like, moved like, talked like Pat," Oprah says. "It was a Beloved moment, if you know what I mean: The daughter who comes back from the dead."

Sources: Oprah.comFox News, ABC News, The Frisky