Jesse Williams Wants to Share the Story of His Great-Great Grandfather's Ascent from Slavery 'with My Children'

In PEOPLE"s exclusive sneak peek at next week's 'Finding Your Roots', the 'Grey's Anatomy' alum discovers that one of his ancestors overcame "unfathomable opposition" to lead a prosperous life

Jesse Williams is in for a surprise when he learns the truth about his great-great grandfather in the newest episode of PBS's Finding Your Roots.

In PEOPLE's exclusive sneak peek at , host Henry Louis Gates, Jr. reveals to the Grey's Anatomy alum on Tuesday's episode, that Williams’ great-great grandfather Isaac was a Black man “almost certainly born into slavery.”

“But as the census shows, when freedom came, Isaac transformed his life,” Gates Jr. adds. “He learned to read, became a landowner, married and raised 10 children.”

For Williams, 42, who taught African and American history in low-income public schools for several years prior to becoming a successful actor, the discovery holds special significance.

Related: How LeVar Burton's Finding Your Roots Journey Made Him Feel Closer to the Father He Hadn't Seen 'in Decades'

“Wow. Got a huge family. All this property. Can read and write. This is an incredible turn of events despite just unfathomable opposition,” he says, adding, “I feel lucky to be able to put a point on it and be able to name it and have a place on the map to point to something to explore further and share with my children."

"It's so much different to be able to have any level of — any level of — precision, any level of actual naming, so that I can sit with it and think about it and say his name and take them with me now," Williams adds. "It's a big deal.”

Related: Maya Rudolph's Shocking Discovery About Her Slave Ancestors on 'Finding Your Roots' : 'I Just Think of My Daughter'

The 10th season of Finding Your Roots so far has been full of revelations for its guests. In the prior episode, Bob Odenkirk learned that in addition to being genetic cousins with Nathan Lane, he's related to King Charles — a "crazy" connection.

“I’m an American. I’m not a monarchist. I don’t believe in, uh, that,” Odenkirk, 61, said to Gates Jr., before learning of his connection to the British monarch. “You know, I feel like it’s a little twisted. I understand why society built itself around monarchs and leaders, and they passed them down through generations."

Likewise, Iliza Schlesinger learned in the same episode she was genetic cousins with friend Sarah Silverman.

“My first thought was like, but she's from New Hampshire!” Schlesinger, 40, quipped. “Oh, my god. That's really cool.”

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Finding Your Roots airs at 8 p.m. ET on Tuesdays on PBS.

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