Joe Manganiello has taken on some legendary roles. Whether portraying werewolf Alcide Herveaux in five seasons of the HBO series True Blood or Big Richie in Magic Mike, the actor has definitely made a name for himself over the past two decades.

But it’s his actual name, specifically his last, that may not actually be his at all. Appearing on PBS’ show Finding Your Roots, where guests have their family tree thoroughly studied by the program’s researchers, host Henry Louis Gates dropped a bombshell on the 45-year-old.

According to Gates, the man Manganiello’s family believed to be his paternal grandfather really wasn’t. “My grandfather was a Black man of mixed race,” Manganiello, who is white, told TV critics during a meeting Thursday (July 28), according to the Associated Press. “That was fascinating.”

Gates, as a result, told him, “You are zero percent genetically related to anyone named Manganiello in the world.”

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That wasn’t all, the show’s research also traced back to the actor’s fifth great-grandfather who was a slave and became free before slavery was abolished in Massachusetts, where Manganiello’s father was born. His father’s family emigrated from Italy.

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

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

The PBS program also probed into Manganiello’s mother’s side of the family, finding that his maternal great-grandmother was a survivor of the Armenian genocide during World War I in which her husband and seven of her children were killed.

Finding Your Roots airs on Tuesdays at 8 p.m. EST.