ATLANTA (CNN) — When Ben Affleck agreed to take part in the PBS documentary series "Finding Your Roots," he probably never imagined he'd learn that one of his ancestors was a slave owner.

In April, the actor admitted via Facebook that he was embarrassed about the discovery and didn't want "any television show" about his family "to include a guy who owned slaves."

Wrote Affleck, "The very thought left a bad taste in my mouth."

As someone who still doesn't know much about her family's history and who has been vowing to finally figure it out for both my daughters and me, I wonder how I would handle what I might find.

It can be more than uncomfortable learning that you are connected to people who have done dreadful things, but writer and best-selling author A.J. Jacobs, who has become a bit of an expert on genealogy through his work spearheading what may be the largest global family reunion in history, says parents are best served by being open and honest about their family.

"I mean, we all have horrible, horrible relatives," Jacobs said, adding that by the eighth generation, our family tree probably has about 4,000 ancestors on it.

"Some of them are going to be absolutely horrible, so it's also a matter of acknowledging it but focusing on the good ones, like making an active choice and saying 'I'm going to be inspired by these relatives, and I know that these ones existed. But if I'm going to follow in anyone's footsteps, I'm going to follow the ones who left the world a better place.' "

Make discovering family history a teachable moment for kids

Nobody would probably have ever known about Affleck's controversial family tree if WikiLeaks had never released hacked emails between Sony Pictures chief Michael Lynton and Henry Louis Gates Jr., the producer of the PBS documentary. From those emails, it was clear Affleck had lobbied for the material to be removed from the program.

The segment about his slave-holding ancestor was ultimately not included when the episode aired, a move that Affleck says he now regrets.

But if Affleck were open to airing the shameful parts of his family's past as well as their proud history, it could have been a teachable moment for his three children.

What children learn when they hear about their past — both the good and the bad — Jacobs said, is primarily that they can chart their own course and don't have to follow the path of what their less-than-stellar ancestors did. They also learn that they are part of something bigger than themselves.

"When you're a kid, you think you're the most important, you're the only person out there, the world revolves around you, and this is just one way to show them no, you are part of this massive world. You are just one link in the chain," said Jacobs, who has done some extraordinary things in his career before trying to break the Guinness record for largest global family reunion.

He spent a year following the teachings of the Bible for his book "The Year of Living Biblically," and in "Drop Dead Healthy," he tried every possible diet and workout in his quest to become the healthiest person in the world.

Research: Knowing family history can be beneficial to children

If Jacobs' argument weren't enough to convince me to finally get off my expletive and chart our my family tree, here's another reason: Research shows that children who have been told about their ancestors and know a great deal about their past are better adjusted and more resilient in the face of challenges.

A study conducted at Emory University and published in 2010 involved asking children a range of questions such as whether they knew where their parents met and where they grew up and went to school.

The authors found that the more children knew about their family history, the higher their self-esteem and the better able they were to deal with the effects of stress.

"Family stories provide a sense of identity through time, and help children understand who they are in the world," the researchers said in their paper.

Related:

Email: Affleck asked PBS to not reveal slave-owning ancestor

Ben Affleck requested that the PBS documentary series "Finding Your Roots" not reveal he had a slave-owning ancestor, according to emails published online by whistleblower site WikiLeaks, and the information never appeared on the program.

(To get started, you can check out sites such as Geni, Family Search, My Heritage and Ancestry. Having any sort of date information is helpful such as the date your grandparents were married, born or died, said Jacobs.)

'Oh, it's Uncle Albert'

Jacobs said there is yet another benefit to teaching your kids about their past: It's a way to get them interested in history.

After his kids learned that they were related to Albert Einstein, it was like, " 'Oh, it's Uncle Albert. Let's figure out what he said,' " said Jacobs.

And as they were reading books by Laura Ingalls Wilder, Jacobs was surprised to learn that his "great, great, great-grandmother" went west on a covered wagon.

"Which I didn't expect for Jews. ... I didn't think Jews and covered wagons mixed," joked Jacobs, who is Jewish.

The discovery made reading and learning about the history so much more personal for his children. "It was like, these were your people who were going across the country."

Jacobs, who is organizing the Global Family Reunion taking place in New York and around the world Saturday, has discovered that his family — in addition to Einstein and Ingalls Wilder — is related to presidents (Barack Obama, Bill Clinton and George H.W. Bush), actresses (Valerie Bertinelli and Jane Krakowski) and musicians including John Legend and the hip-hop artist Ludacris.

Jacobs informed Ludacris that he was 1/16 Jewish.

"And I loved telling him that," Jacobs said. "He was a little taken aback. ... He's like, 'What? I thought I was African-American.' "

That's the beauty of genealogy, he said. "It's eye-opening, and it makes you much more aware how interconnected we all are. It's much harder to be racist and narrow-minded when you see how closely linked all the races are."

'They're my cousins. They'll understand'

Perhaps the only downside Jacobs has experienced to this whole "we are one big family" project is that it can backfire.

Case in point: He tells the story of being at a restaurant with his son and his son's friend, who was aware of Jacobs' genealogy pursuits.

When his son's friend dropped his napkin on the floor, Jacobs asked him to pick it up and talked about the people who work at the restaurant and why it would be great not to make their job any tougher.

To which the child replied, " 'Well, they're my cousins. They'll understand,' " said Jacobs. "I was like, 'that's the wrong message.' "

Have you shared your family history with your children? Share your thoughts with Kelly Wallace on Twitter @kellywallacetv or CNN Parents on Facebook.

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