Blue Bloods spinoff Boston Blue made a decision to recast Donnie Wahlberg's onscreen son with Mika Amonsen. The hit series, which premiered in 2010, followed the lives of the Reagan family, many of whom work for the NYPD under the leadership of NYC police commissioner Frank Reagan (Tom Selleck). Frank's father, Henry Reagan (Len Cariou), was also central to the show, alongside Frank's children: daughter Erin Reagan (Bridget Moynahan) and sons Danny (Wahlberg) and Jamie Reagan (Will Estes). Danny was previously married to Linda Rose Reagan (Amy Carlson), with whom he shared sons Jack and Sean, before her death. The role of Danny's youngest son was played by Andrew Terraciano for the entirety of the show's 14 seasons. After Blue Bloods came to an end in 2024, CBS announced a spinoff titled Boston Blue. Wahlberg's character is at the center of the spinoff, which picks up as the former NYPD officer takes on a position with the Boston P.D. He is then paired with detective Lena (Sonequa Martin-Green), the eldest daughter of a prominent law enforcement family. Boston Blue's Recasting of Donnie Wahlberg's Son From 'Blue Bloods' Explained In July 2025, Amonsen was added to the cast as Sean. "We love Andrew and the work he did over the years on Blue Bloods. Really, it came down to we're telling a new chapter in both of their lives," Margolis told Variety in October 2025 about the decision. "It's not just Sean who has joined the family business as it were and is turning over this new leaf, but it's also now Danny Reagan is the father [of] a cop, which he's never been before." Margolis called the switch "an organic opportunity to bring in a new performance with a new energy, to help dramatize that change." The writers' room was looking forward to "new storytelling lanes to explore" with the spinoff series. "It is the same character, it's the same relationship, but it's also completely different," he continued. "We love what Mika has brought to Sean, this vulnerability, yet this desire to prove himself. It's just been great to watch it come to life." Keep scrolling for everything to know about Amonsen amid the recast: How Did Mika Amonsen Get His Start? Seacia Pavao/CBS (C)2025 CBS Before acting, Amonsen was the lead guitarist of a Toronto-area rock band. The group revealed a 10-track album and opened for Kim Mitchell before Amonsen opted to explore acting instead. "It's a rush and you feel heard. Also, the idea of escape," Amonsen told Numero One in February 2025 about his love for music. "I was home schooled in a town with five hundred permanent residents. The idea of breaking free, making music, socializing and hitting the road was a fantasy. Even though we had some success, it quickly became clear to me that music as a full-time pursuit is by far one of the hardest. I sympathize with musicians deeply." What Else Will Mika Amonsen Appear In? Michele Crowe/CBS (C)2025 CBS After starring opposite Alan Ritchson in Prime Video's hit series Reacher, Amonsen was cast alongside Patrick Dempsey and Rick Hoffman in Eli Roth's horror film Thanksgiving. He also joined Corin Hardy's Whistle, alongside Dafne Keen and Nick Frost. "I really enjoy playing eccentric characters who fit into the 'bad guy' category because they're so far from the norm. I'm naturally more introverted, so the more outrageous and unhinged the character is, the more excited I get to step out of me," Amonsen continued in February 2025. "[I love] tragic heroes for sure. I'm attracted to flawed people. There's something beautiful about a character that means well, loses their way and may or may not find redemption. Perfection is overrated I think in any medium. Those are the stories that pique my interest and I feel fortunate that at this point in my career I'm beginning to be offered those types of roles." Which Role Did Mika Amonsen Take Over? CBS (3) Danny's son Sean is an integral part of CBS' Boston Blue, a spinoff of Blue Bloods. Fans of the long-running series may be surprised to see Amonsen as Sean after Terraciano originated the role. Coshowrunner Brandon Margolis defended the casting decision while noting that he "loved" watching Terraciano "grow up on TV," telling TV Insider in October, "It creatively made sense to find an actor with a different energy." He concluded: "And to your point, yeah, it was a gamble to open the show on a new face - two new faces, actually - but the story required us to love him right away. Opening with that heroic moment that has a tragic end was the right way to pull Danny Reagan into this world." 'Blue Bloods' Family Guide: Meet the Reagans Amid 'Boston Blue' Spinoff What Is Sean's Story in Blue Bloods' Spinoff 'Boston Blue'? Christos Kalohoridis/CBS (C)2025 Boston Blue focuses on Sean's attempt to rise the ranks alongside friend and coworker Jonah (Marcus Scribner). He will receive help from Danny, who chose to stay in Boston to look after his son and continue working with Lena for the Boston PD. "Sean has relocated to Boston