The Winchesters is adding another familiar face for fans of Supernatural.

The prequel series has locked in Gil McKinney for an upcoming episode of the freshman drama, TV Line reports.

If you watch Supernatural online, you know McKinney portrayed Dean and Sam's paternal grandfather Henry Winchester.

McKinney read a letter that Henry wrote him on The Winchesters Season 1 Episode 1, which premiered earlier this week as The CW's most-watched series debut of the season.

Henry is described as “the intellectual patriarch of the Winchester clan."

“Having come from a long line of Men of Letters, Henry fully dedicated his life to the institution," reads the description.

"However, when a Men of Letters’ mission leads to Henry’s untimely death, his absence and the secrecy surrounding his life inside the organization creates an unrepairable rift in his family."

McKinney is the latest addition to the series, and his casting comes days after it was revealed that Tom Welling would be joining the cast as Samuel Campbell.

The Winchesters takes viewers back in time to unveil the origins of John and Mary Winchester.

"Before Sam and Dean, there were their parents, John and Mary. Told from the perspective of narrator Dean Winchester (Jensen Ackles, Supernatural), The Winchesters is the epic, untold love story of how John Winchester (Drake Rodger, The In Between) met Mary Campbell (Meg Donnelly, American Housewife) and put it all on the line to not only save their love, but the entire world," the logline for The Winchesters teases.

"When John returns home from fighting in Vietnam, a mysterious encounter sparks a new mission to trace his father’s past."

"In his journey, he crosses paths with 19-year-old demon hunter Mary, who is also searching for answers after the disappearance of her own father."

"Together, the two join forces with young hunter-in-training Latika (Nida Khurshid, Station 19) and easygoing hunter Carlos (Jonathan “Jojo” Fleites) to uncover the hidden truths about both their families."

"Their investigation leads them to a rare book emporium, whose owner Ada (Demetria McKinney, Tyler Perry’s House of Payne) takes an interest to the occult and could provide the missing pieces to their puzzle.

"But secrets run deep for both the Winchesters and Campbells, and despite the best efforts of John’s mother Millie (Bianca Kajlich, Legacies) to protect her son from pursuing a dangerous life of demon hunting, John and Mary are both determined to work together to uphold their families’ legacies while beginning to form a family of their own."

Catch new episodes Tuesdays at 8 p.m. on The CW.

Paul Dailly was an Associate Editor for TV Fanatic.Follow him on X.