Mark Harmon’s Sons Are All Grown Up, And One Played Young Gibbs On ‘NCIS’

The snapshot on our card was taken in 1968, and the teenager in it had a lot to live up to. Mark Harmon was 16 that summer and playing football at the Harvard School in Los Angeles, and his father was Tom Harmon, the Michigan halfback known as “Old 98” who won the 1940 Heisman Trophy. Within a few years the son would be starting at quarterback for UCLA. A cold call to Dragnet creator Jack Webb would then start the acting career that eventually made him Leroy Jethro Gibbs.

Mark is 75 now, and his own boys are long past the age he was in that photo. He and Pam Dawber, also 75, raised two sons, Sean and Ty, about as far from the Hollywood spotlight as two famous parents can manage. One of them grew up to play a young version of his father on NCIS. The other went to work behind the camera. And the family’s newest chapter has been the most surprising one yet.

How Did A Heisman Winner’s Son End Up On ‘Adam-12’?

Football was the family business first. Tom Harmon led the nation in scoring in 1939 and 1940, and in his senior year he won both the Heisman and the Maxwell Award before going on to fly in World War II and build a long career as a sportscaster. Mark, born September 2, 1951, in Burbank, followed him onto the field. After two seasons at Pierce College he transferred to UCLA, where he started at quarterback for the 1972 and 1973 Bruins. In his senior year he received the National Football Foundation’s award for all-around excellence, the same organization that gave him its highest honor in 2019.

Acting came through family too. Mark’s older sister Kristin had married Ricky Nelson, which made Ozzie and Harriet Nelson her in-laws, and they gave Mark his first job on an episode of Ozzie’s Girls. (Kristin and Ricky’s marriage, and the family heartbreak that followed, is a story of its own.) For his next break, Mark picked up the phone and called Jack Webb, the man behind Adam-12 and Emergency!. “We talked for a couple minutes, and he said, ‘Why don’t you come in and talk to me?'” Harmon recalled on The Fifth Column podcast, as TVLine reported. By 1975 he had guest roles on both shows, and in 1978 Webb made him the lead of Sam, a short-lived series about an LAPD officer and his police dog.

Another phone call changed his personal life. Harmon has credited a cold call for his first date with the Mork & Mindy star, and he and Pam Dawber married on March 21, 1987. A year later, the first of their two sons arrived.

Which Harmon Son Stepped Into Gibbs’s Shoes?

Sean Harmon was born April 25, 1988, in Burbank, which makes him 38. He found his way into the business through stunts rather than straight acting. According to People, he became a stunt performer and coordinator who specializes in fight scenes, and he has credited 12 years of Muay Thai kickboxing for that work. “Both of my parents are actors and my grandmother before my dad,” he told the Stunt Hustle podcast. His grandmother was Elyse Knox, the 1940s actress and model who married Tom Harmon.

In 2008 a director on NCIS asked if Sean could play the younger Gibbs in flashbacks. He made his debut in the Season 6 episode “Heartland” and returned a handful of times over the next twelve years, most recently in Season 18 in 2020, the same year he appeared in the show’s 400th episode. His father made no secret of how much it meant to him. “I’m proud of him taking his work seriously and how he approaches being an actor,” Mark told Entertainment Tonight, “not just on this show, [but] just what he has chosen to try to do in his life’s work.”

Sean married Courtney Prather, his producing partner, in Costa Rica in November 2022, more than a year after they announced their engagement. If you watched those flashbacks and thought you were seeing a young Mark Harmon, you were not far off. His little brother, though, took a very different path.

Why Does Ty Harmon Stay Out Of The Spotlight?

Ty Christian Harmon was born June 25, 1992, in Los Angeles, and he is 34. People has described him as a screenwriter who prefers to work behind the scenes. In 2012 he and Sean made a short film together called Catholic Schoolgirl Chainsaw Showdown. Hello! reported in April 2026 that his credits since then include work on Apple TV’s space drama For All Mankind. Ty married Madeline Harmon in February 2021 after five years together, and he has kept almost everything else about his life offline.

That privacy was the plan from the start. “We’re not trying to keep something secret, but if you don’t want it totally exploited by the press, you have to,” Dawber told People in 1987, the year she and Mark married. After My Sister Sam ended in 1988, the year Sean was born, the roles slowed down by choice, and as she turned 75 last month she was still glad she stopped chasing the business. Mark said he chose NCIS partly because it let him stay close to home. “It was important to be able to make pancakes on Saturday morning,” he told People in 2023. Looking at his sons now, he has said, “both our boys have done well and hopefully made smart choices.”

Mark has said the family simply prefers to “stay home. A lot.” But in 2024 one of those boys pulled his father back to work, and it started with an idea Sean had been carrying around for years.

What Did Sean Harmon Bring Back To His Father?

The prequel NCIS: Origins, which follows a young Gibbs in 1991, began with Sean. “The idea was Sean’s and it just made sense that there was a new story to tell,” Mark told Forbes in October 2024. Sean said the concept came to him while he was playing the younger Gibbs in those flashback episodes. “This is an idea we worked on for a long time and just really happy to finally be at this point in the process,” he told Entertainment Tonight. Father and son became executive producers together, and Mark narrates the series as the older Gibbs.

Many fans assumed Sean would take the lead role himself, but Austin Stowell got the part. “I just think he made a choice and had to make a decision in some ways,” Mark told Variety, as TV Insider reported. “He likes executive producing.” Sean did step back in front of the camera this fall, though not as Gibbs. On October 13, 2026, he guest starred in the Season 3 episode “My Own Worst Enemy” as FBI Agent Casey Bloom, a role TV Insider announced in September. A week later, his father shared the screen with Michael Weatherly for the first time in a decade, in the reunion episode fans had been waiting years to see.

The biggest news in the family, though, came off camera. Sean and Courtney welcomed a son on May 22, 2025, and Courtney introduced him on Instagram a month later. “1 month with you. Cooper Knox Harmon,” she wrote. His middle name carries on Elyse Knox, the actress grandmother Sean credited with starting it all, which makes the boy in that 1968 football photo a grandfather now. Sean summed up what that boy grew into in a single line to Entertainment Tonight. “I like to think he made me the man I am today.”