Actor Joe Manganiello learned a shocking revelation about his paternal grandfather during this season of PBS’s Finding Your Roots.

In the upcoming episode, the Magic Mike star uncovers some mysteries about his family that were so surprising, host Henry Louis Gates Jr. had to call Manganiello with the news so he wouldn’t find out first during taping.

Joe Manganiello learned that his paternal grandfather wasn't who everyone thought he was.

According to the AP, as discussed during PBS’s TCA tour panel, Manganiello learned that his paternal grandfather was a mixed-raced Black man.

“My grandfather was a Black man of mixed race,” said Manganiello. “That was fascinating.”

"You are zero percent genetically related to anyone named Manganiello in the world," host Henry Louis Gates Jr. told Manganiello.

Gates went on to uncover that the actor’s fifth great-grandfather was a slave who became free before slavery was abolished in Massachusetts, where Manganiello’s father was born outside of Boston.

Manganiello found out his distant relative joined the Continental Army and fought alongside other Blacks for the colonies against the British in units that were non-segregated.

“None of us would have guessed that if we’d had 10 years of guessing,” the actor said. “If Manganiello’s not my last name, what is?”

Manganiello also uncovered a mystery from his mother's side of the family.

In the episode, Manganiello also uncovers some information about his maternal great-grandmother.

Gates reveals to the actor that his great grandmother on his mother’s side was a survivor of the Armenian genocide during World War I, which killed her husband and seven children. Although she was shot, she played dead and escaped with her eighth child, who later drowned while they traversed the Euphrates River.

Growing up, Manganiello was told his great-grandmother was incarcerated and met a German officer stationed at the camp.

He said she became pregnant by the officer, who later returned to Germany without her. The actor’s aunt had a picture of the man, which was later lost.

“We had nothing to connect us being German other than this,” he said.

The show's DNA researchers found that the actor's mother and aunt were the children of the half-German baby.

“That was a really profound moment for me,” he said.

The new season of Finding Your Roots begins Jan. 3. Among those featured are Oscar winners Viola Davis and Julia Roberts, as well as Carol Burnett, political activist Angela Davis, and actor Danny Trejo.