Who is Claire's brother in Outlander: Blood of My Blood? Fans are convinced they already met him — grown up, in the original series

Outlander: Blood of My Blood, Starz's prequel about the parents of Jamie and Claire, is midway through its second season, which premiered September 18, 2026, and it's still sitting on the biggest secret it created. Season 1 gave Claire a younger brother she never knew about. Showrunner Matthew B. Roberts says the plan for him dates back to the pilot pitch, and fans have spent a year arguing that the original Outlander already introduced him as an adult.

Roberts isn't saying who's right, but he is promising a reaction.

"I think heads might explode…but I'm not going to tell you!"

— Matthew B. Roberts, showrunner, to Decider, via BIC News

How Claire got a brother

The original series told us Claire's parents, Henry and Julia Beauchamp, died in a car accident when she was a child. Episode 6 of the prequel, "Birthright," which aired September 5, 2025, reveals they didn't. Henry (Jeremy Irvine) and Julia (Hermione Corfield) were pulled through time to 1714 Scotland, and Julia was pregnant.

Episode 7, "Luceo Non Uro," handled the birth and the paperwork, per Comic Basics:

• The birth: Julia's son is born on July 5, 1714.
• The deal: Julia slept with Simon Fraser, Lord Lovat (Tony Curran), so he would believe the child was his, and let him think the boy would be baptized Simon Fraser.
• The real name: Brian Fraser (Jamie Roy), Jamie's future father, helped Julia hold a private baptism first, where the baby was christened William Henry Beauchamp. Lovat's public ceremony came after.

So Claire's brother has two names, one on a secret record and one on the record Lovat knows about. Season 2 opened with Julia and William back at Lovat's Castle Leathers, where Lovat is overjoyed to have the boy he believes is his son and heir, per But Why Tho. Henry, meanwhile, has landed in 1924, locked in an asylum.

The two leading theories

Fans have narrowed it down to two men from the original series:

• Simon Fraser, the "Young Fox": Lovat's son and heir, introduced in Outlander season 2's "The Fox's Lair." The case for him: the baby was publicly baptized Simon Fraser, and Lovat already treats him as his heir. In Dragonfly in Amber, Claire describes Simon as around Jamie's age.
• Willie Fraser: Jamie's older brother, the namesake of Jamie's own son William. This theory has Brian and Ellen adopting the baby. The catch: Willie died of smallpox as a child, so Claire never met him, as CinemaBlend points out.

The Young Fox theory has its own problem. The Simon of the original series was reportedly Lovat's son with Margaret Grant, a woman the show never introduced, and born about a decade after Julia's baby.

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Why Simon is the one fans mean

Only one of the two fits the headline's version of the theory, a brother Claire actually met as an adult. That's the Young Fox. In "The Fox's Lair," Lovat treats his timid son terribly and humiliates him in front of others, and the son eventually surprises everyone by standing up to his father and pledging loyalty to the Jacobites, per Soap Central.

If the theory holds, Claire met her own little brother at the Fox's Lair and watched a man who wasn't his father humiliate him, and neither of them knew.

The prequel keeps adding pressure. In season 2's sixth episode, "Small Mercies," which aired October 23, Lovat is revealed to have poisoned wine to leave Ellen and Julia infertile, and Ellen loses a pregnancy, per Comic Basics' recap. The episode ends with Arch Bug helping Henry and Julia reach each other.

Roberts said his plan was "in the pitch." Season 2 runs through November 20, so there are four episodes left for it to land.

Previously we wrote: Is The Lowdown a true story? The real man died in 2015 — and his family says FX is 'muddying fact and fiction'