Harrison Ford's good friend in Yellowstone prequel 1923 is the cyborg that tried to kill Arnold Schwarzenegger in Terminator 2. Actor Robert Patrick has been added as a series regular as the show beefs up its cast for filming.

Patrick — whose character name in T2 was T-1000 — is latest in a flurry of cast additions for 1923 ahead of its December premiere on Paramount+. Yellowstone and 1883 fans also now know who will play Spencer Dutton, the youngest of two sons fathered by Tim McGraw's James Dutton in 1883. We also know who Ford and Helen Mirren are playing, but first, the newest roles:

Deadline reveals that Patrick will join as Sheriff William McDowell, a friend of the Dutton family. While some characters portrayed in Yellowstone prequels have been based on real people (Billy Bob Thornton's Jim Courtright, for example), there's no research to indicate McDowell was a notable historical figure. Patrick's past credits include Sons of Anarchy, True Blood and the X-Files.

The casting of Brandon Sklenar as Spencer Dutton in 1923 is not as remarkable, but perhaps more interesting. He'll play an older version of a character fans know only through flashback scenes in Season 4 of Yellowstone. There was no confirmation of who the other boy in the flashbacks even was — throughout 1883, James and Margaret Dutton (Faith Hill) had just one son — but a note from Paramount clarifies.

Spencer is the nephew of Jacob Dutton (Ford) and son to James Dutton. That means he's also brother to John Dutton, played be Audie Rick in 1883. Missing is a character who represents James and Margaret Dutton, which is ominous. In 1923, John Dutton Sr. will be played by James Badger Dale.

The remainder of cast announcements is below. Worth noting is Sklenar's Spencer Dutton character description: He will represent the damage World War I had on Americans, specifically those who served. While stopping short of describing him as a soldier in the war, he's said to have seen some of the horrors of WWI.

Darren Mann: Jack Dutton, John Dutton Sr.'s son, great nephew to Jacob Dutton.
Marley Shelton: Emma Dutton, wife to John Dutton Sr., mother to Jack.
Michelle Randolph: Elizabeth Strafford, a "feisty and capable young woman set to marry into the Dutton family.
Brian Geraghty: Zane, a loyal ranch foreman.
Aminah Nieves: Teonna Rainwater, a young woman at a government residential boarding school.
Julia Schlaepfer: Alexandra, a British woman who meets one of the Duttons abroad.
Sebastian Roché: Character unknown, confirmed by Deadline.

Yellowstone: How Is James Dutton Related to John Dutton?

The relationship between John Dutton on Yellowstone and James Dutton on 1883 was mostly a bar argument until a very pivotal line of dialogue from Ep. 10 of the Tim McGraw show. Suddenly fans wanted to know who the seventh generation Dutton is. We've illustrated the relationships below and found the fact that is tripping people up in the quest to make sense of this family tree.