"Siblingship is an emotional feeling as much as it is biological feeling. You can have a sibling relationship with someone who's not related with us, and we can have a sibling whom we feel no relationship with," said Belkin.
While Winfrey seemingly embraced her sister within a few months of knowing her, Belkin cautions others to take as much time as they need to decide how they will proceed once they know the truth.
"People love Oprah and care about her, and I think you know there's going to be pain involved," said Belkin. "And what she can do is what she's always done -- use this to help other people."
On her show Monday, Winfrey made it clear that she wanted to be the one to tell the public her family secret.
"Needless to say, it's something you need to process when it happens, and my family and I agreed that we wanted to do it on our own terms and not have it be some big tabloid spectacle," Winfrey said.
Mary DeMuth, author of "Defiance Texas Trilogy," a three-book fiction series on family secrets, and a memoir, "Thin Places," said that people today are much more willing to share secrets freely.
"Nowadays people are much more apt to authenticity," Demuth said.
DeMuth's research into family secrets led her to create a blog where people can anonymously write about their family secrets. Since its inception in 2009, the blog has had nearly 300 postings of secrets revealed.
"Some say you can't move on until you know the truth," said DeMuth. "But you have to ask, so what if you know the truth? You still have the decision to make of either moving forward or not."
Twilla Fontenot, 48, of Dallas, was 16 years old when she came home one day to find a stranger sitting at her family's kitchen table, whom her mother introduced as Fontenot's stepbrother.
"People react to situations differently," she said. "When you have chaos in the household, when you have one more thing thrown at you, it just didn't soak in for me."
Until then, Fontenot had no idea her father had a son from a previous marriage. And it wasn't until nearly 20 years after that brief introduction that she decided to reunite with her stepbrother.
"I was curious to know what he would be like. For some reason, I really, truly was hoping that my father would build a connection with his son," said Fontenot.
But it wasn't easy to build a relationship with her stepbrother. And although she still sees him occasionally, she said she's unsure whether it brought the closure she thought it might. She feels much closer to her other siblings, with whom she was raised.
"When you haven't been raised with a sibling, there's not those connections, those memories and experiences you go through in life," she said.
ABC News' Lara Salahi and Emily Friedman contributed to this report.