With CBS planning to debut Boston Blue, the first-ever official spinoff of its long-running drama Blue Bloods, one of the most debated details is the fate of Sean Reagan, the youngest member of the Reagan family.
CBS has also confirmed on July 9, 2025, that the character will be appearing in the new series, but with a twist. Mika Amonsen is now set to take over Sean Reagan, a character played by Andrew Terraciano across all 14 seasons of the original show.
This casting represents a change of direction in the franchise, with an idea of an alternate identity for a returning character.
According to People Magazine, the production itself started in early July, and the first table read was on July 8, 2025. The show will premiere in the Fall of 2025, replacing Blue Bloods on its traditional Friday 10 pm slot on CBS.
A fresh start for Sean Reagan in Boston Blue
Mika Amonsen is joining the cast to replace Andrew Terraciano, who portrayed Sean Reagan throughout 14 seasons of the original series. Mika Amonsen is a Canadian actor, best known for his work in Eli Roth’s horror film Thanksgiving (2023) and the Amazon series Reacher.
Entertainment Weekly stated that Sean will have a character arc, and his story continues with him starting a new journey in Boston, having joined the Boston Police Department as a patrol officer.
"[Sean Reagan is] relocated to Boston to start a new chapter as a Boston PD patrolman. Sean committed himself to pursuing his family's legacy but wanted to do so on his own terms, which meant joining a department outside of his hometown. Danny's decision to stay in Boston gives this father and son duo a chance to reconnect on a deeper level," as per CBS.
Sean has decided that he would continue the family tradition of law enforcement, but chose to leave the city of New York behind to make his way in life. The recasting is part of the network’s broader creative direction for the spinoff, allowing the story to move forward with an already-established version of Sean in his new environment.
This change in Sean Reagan's character also opens up the possibility of new storylines, particularly on the relationship between Sean and his father, Danny Reagan, still a prominent actor in the series.
Family values remain central in Boston Blue
Although new characters and settings were introduced, Boston Blue is set to keep the essence of what made Blue Bloods family-ridden in spirit. Detective Danny Reagan, played by Donnie Wahlberg, will also be an ongoing presence throughout the show. The character provides a point of familiar emotionality within the changing cast.
In a conversation with Fox News Digital, Wahlberg hinted that every person engaged in the drama crime series “fought so hard” to see it stay alive, but the Reagan family customs would be continued in the Boston Blue.
Blue Bloods was a drama that followed the Reagan family’s involvement in the New York Police Department. Wahlberg informed Fox News Digital that he cannot say too much about the upcoming crime drama, but Reagan is always just a “phone call away.”
“It was definitely a challenge to take on this opportunity, but I kept saying to myself, you know, if I’m really sincere about wanting ‘Blue Bloods’ to carry on, here’s an opportunity to do it."
He added:
“Now, it’s just Danny going to this new world, but I can’t say a lot about it — but I could say, if he’s a Reagan, it will never be just Danny. There’ll always be a Reagan a phone call away. And the traditions that the Reagans have, Danny wouldn’t abandon those traditions.”
The last episode of Blue Bloods premiered on December 13, 2024, on CBS. Wahlberg, Tom Selleck, Will Estes, and Bridget Moynahan were the stars of the hit series.
With Boston Blue being a Blue Bloods extension to the franchise, the show is both a continuation of another popular franchise and a step towards new possibilities.
The addition of Sean Reagan, now played by Mika Amonsen, helps bring in continuity and emotional tie, as he reconnects with his father, Danny Reagan.
Boston Blue is scheduled to air in Fall 2025.