You’ve seen the photos. Two kids from Cambridge, Massachusetts, clutching a pair of Oscars for Good Will Hunting in 1998. They look like brothers. They act like brothers. They even shared a bank account when they were struggling actors because, honestly, who else could you trust that much?
But the question persists: Are Ben Affleck and Matt Damon related in a way that goes beyond just being "best buds"?
The answer is a weird, historical "yes." But don't expect to see them at the same Thanksgiving table because of it. Unless you're counting a dinner party from nearly 400 years ago.
The 10th Cousin Connection
In 2009, the New England Historic Genealogical Society (NEHGS) decided to do some digging. They’re the oldest genealogical society in the country, so they aren't exactly prone to clickbait. Researchers Chris Child and Rhonda McClure spent time tracing the family trees of the two stars and found a common link that traces back to colonial America.
It turns out Ben Affleck and Matt Damon are tenth cousins, once removed.
That sounds official, right? Basically, it means they share a set of 10th-great-grandparents. If you’re trying to picture that in your head, imagine going back eleven generations. It’s a massive distance. You likely have thousands of tenth cousins walking around right now that you’ve never met and definitely wouldn't recognize at a grocery store.
The Ancestor: William Knowlton Jr.
The man responsible for this Hollywood lineage was a fellow named William Knowlton Jr. He was an English bricklayer who hopped on a ship and settled in Ipswich, Massachusetts, back in the 1630s. He died in 1655, probably having no idea that his DNA would eventually produce a Batman and a Jason Bourne.
- Ben Affleck descends from Knowlton’s son, Thomas.
- Matt Damon descends from Knowlton’s daughter, Mary.
They are quite literally "keeping it in the family," even if that family tree has more branches than a redwood forest.
Why Do They Look So Much Alike?
Genetics is a funny thing. Tenth cousins share about 0.0001% of their DNA. That is effectively zero.
The resemblance people see—the square jaws, the Boston "vibe," the shared mannerisms—is almost certainly a result of growing up two blocks away from each other rather than William Knowlton’s bricklaying genes. They met when Ben was 8 and Matt was 10. They shared the same schools, the same drama teachers, and the same obsession with making it in Hollywood.
Sometimes environmental "relatedness" is stronger than the biological kind.
It Gets Weirder: The Presidential Ties
If you think the Damon-Affleck connection is a stretch, wait until you see who else is in the mix. The NEHGS researchers found that Ben Affleck is actually more closely related to Barack Obama than he is to Matt Damon.
Affleck is an 11th cousin to the 44th President through the Hinckley family of Cape Cod.
Matt Damon isn't left out of the elite circle, either. His lineage reportedly connects him to at least nine U.S. Presidents, including both Bushes and Theodore Roosevelt. It seems the "Cambridge homeys" come from a long line of people who really like being in charge.
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The "Finding Your Roots" Controversy
We can't talk about Ben Affleck’s ancestry without mentioning the 2015 hiccup on the PBS show Finding Your Roots. While the show confirmed many of these distant ties, it also uncovered that one of Affleck’s ancestors was a slave owner.
Affleck famously asked the producers to leave that part out. It caused a huge stir when the Sony email hack revealed the request.
Eventually, Ben owned up to it, saying he was embarrassed. It’s a reminder that when you start digging into a family tree that goes back to the 1600s, you’re going to find some stuff that isn't as heartwarming as a "BFF" story.
Does the Relation Actually Matter?
Kinda. But mostly no.
In the world of genealogy, once you get past third or fourth cousins, the "relation" is mostly a trivia fact. However, for two guys who have spent their entire lives being inseparable, finding out they actually share a common ancestor is the ultimate "I told you so."
When the news broke back in 2009, Matt Damon joked in interviews that he "always felt like they were kin." It’s a sentiment that fits their brand perfectly.
How to Check Your Own Famous Connections
If you’re curious if you’re also 10th cousins with a movie star, you don't necessarily need a team of historians. Most people with deep colonial New England roots (the "Yankee" lines) are almost certainly related to multiple celebrities and presidents.
- Start with the 1850 Census: This was the first year they listed everyone’s name, not just the head of the household.
- Look for New England Surnames: Names like Knowlton, Hinckley, or Emerson often lead to these massive, interconnected trees.
- Use the NEHGS Database: If your family lived in Massachusetts in the 17th century, the American Ancestors database is the gold standard.
At the end of the day, Ben Affleck and Matt Damon being related is a fun footnote in a legendary friendship. They didn't succeed because they shared 0.0001% of their DNA; they succeeded because they were two kids from Boston who refused to take "no" for an answer.
If you want to dive deeper into your own tree, start by documenting your grandparents' full names and birthplaces. Often, the path to a 17th-century bricklayer starts with a single dusty birth certificate in your own attic.
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Actionable Insight: If you have ancestors who settled in Essex County, Massachusetts, before 1700, there is a high statistical probability that you are also a distant cousin to either Ben Affleck or Matt Damon. You can verify this by searching for "William Knowlton Jr." in public trees on sites like FamilySearch or Wikitree to see if your lineage intersects with the Knowlton branch.