You’ve seen them together for decades. From the gritty streets of Southie in Good Will Hunting to the high-stakes boardroom of Air, the bond between Matt Damon and Ben Affleck feels less like a Hollywood "work friendship" and more like, well, brotherhood. They share an Oscar. They share a production company. They even shared a bank account back when they were struggling actors trying to scrape together enough change for subway fare.
But are they actually brothers? No. Are they cousins? Honestly, the answer is a lot more complicated than a simple yes or no.
If you’ve ever wondered are matt damon and ben affleck related by blood, you aren't alone. It’s one of those trivia nuggets that resurfaces every few years on social media, usually accompanied by a "mind-blown" emoji. The truth involves a centuries-old paper trail, a bricklayer from the 1600s, and a genealogical discovery that links some of the most famous faces in the world.
The Genealogical Deep Dive: 10th Cousins Once Removed
Back in 2009, researchers at the New England Historic Genealogical Society (NEHGS) decided to dig into the family trees of Boston’s favorite sons. What they found wasn't just a coincidence—it was a literal connection.
It turns out Matt and Ben are tenth cousins, once removed.
Basically, they share a common ancestor named William Knowlton Jr. He was an English bricklayer who hopped across the pond and settled in Ipswich, Massachusetts, way back in the 1630s. If you’re trying to wrap your head around what "tenth cousin" means, don't worry. It’s distant. Really distant.
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To put it in perspective:
- Your first cousin shares a grandparent with you.
- Your second cousin shares a great-grandparent.
- By the time you get to the tenth level, you’re looking at a common ancestor from nearly 400 years ago.
So, while they are technically "blood relatives," they didn't find out about it at a family reunion. They found out from a press release. Most people in the United States who can trace their lineage back to colonial New England are probably related to each other at a similar distance. It’s just that most of us don't win Academy Awards with our tenth cousins.
The Famous Family Web
Ben Affleck’s family tree is particularly crowded with heavy hitters. According to the same NEHGS study, Ben isn't just related to Matt. He’s also a distant cousin of Barack Obama and the late Princess Diana.
Genealogist Chris Child, who spearheaded the research, noted that when you have deep roots in New England, these types of overlaps are actually fairly common. Still, it adds a layer of "destiny" to a friendship that has defined both of their lives.
More Than Blood: The "Real" Relationship
While the "tenth cousin" thing is a fun dinner party fact, the actual reason people ask are matt damon and ben affleck related is because of how they act. They behave like family.
They met when Ben was 8 and Matt was 10. They lived two blocks away from each other in Cambridge, Massachusetts. In a town where "townies" stay tight, these two were the ultimate example. Their moms—Nancy Carlsson-Paige and Chris Affleck-Boldt—were both in the education world and encouraged the boys to hang out.
The Fight That Bonded Them
There’s a legendary story Matt Damon tells about a schoolyard fight that changed everything. Matt was getting into it with a much bigger kid on a snowy field. Out of nowhere, "little" Ben Affleck tackled the guy, putting himself at risk to save his friend.
"I remember that was a big moment," Matt told Conan O’Brien years later. "He will put himself in a really bad spot for me. This is a good friend."
That’s the kind of loyalty you usually only see between siblings.
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The Shared Bank Account Era
Before they were A-listers, they were just two kids with a dream and a very unusual financial arrangement. They literally had a joint bank account.
They used it to fund their trips to New York for auditions. If one of them got a part in a TJ Maxx commercial, the money went into the pot. It was a "we both make it or neither of us makes it" mentality.
Think about that. Would you share a bank account with your tenth cousin? Probably not. You’d barely share a Netflix password with a second cousin. This level of trust is why the world assumes they must be related.
Why This Connection Matters in 2026
In an industry known for "fake" relationships and "PR couples," the Damon-Affleck connection stands out because it’s survived everything. Divorces, rehab stints, box office bombs, and massive successes.
They’ve moved past being just friends or even business partners. With their company, Artists Equity, they are trying to change how Hollywood pays its crew and actors. They are still working side-by-side, just like they did in 1997.
Common Misconceptions
- Are they brothers? No. Casey Affleck is Ben’s only brother. Matt has a brother named Kyle who is an artist.
- Did they grow up in the same house? No, but they were only two blocks apart on Pearl Street.
- Is their "feud" real? If you see them bickering on Jimmy Kimmel, it's a bit. It’s been a running joke for nearly 20 years.
The Verdict on Their DNA
So, are they related?
Technically, yes. They share a 10th-great-grandfather.
Practically, no. They aren't family because of William Knowlton the bricklayer. They’re family because they spent their teenage years on a Greyhound bus to Manhattan, dreaming of a life they eventually built together.
If you’re looking to dive deeper into their history, you should check out the archives of the New England Historic Genealogical Society. They’ve mapped out the lineages of dozens of celebrities, and the results are often weirder than you’d think.
For now, the best way to see their "family" dynamic in action is to watch their recent collaborations. You can really see the shorthand they have with each other—it's a type of communication that only comes from 40 years of being in the trenches together.
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Next Steps for You:
If you're a fan of the duo, look up the "Finding Your Roots" episode featuring Ben Affleck (Season 2). While it doesn't focus solely on Matt, it gives a massive amount of context regarding the New England ancestry that connects them both. You might even find out you're their eleventh cousin!