Explaining Boston Blue’s Surprising Switch for Donnie Wahlberg’s Son on ‘Blue Bloods’

Boston Blue has worked hard to win over Blue Bloods fans, but one decision still raises questions: recasting Danny Reagan’s son, Sean.

On Blue Bloods (2010–2024), Donnie Wahlberg’s Danny Reagan was a fan favorite. His youngest son, Sean, was played by Andrew Terraciano for all 14 seasons. When the original series ended in December 2024, CBS announced a spinoff, Boston Blue, centered on Danny’s next chapter.

The new series moves Danny to the Boston Police Department and pairs him with a new partner, Detective Lena (Sonequa Martin-Green). Sean also relocates to Boston, following the family legacy by becoming a Boston PD patrolman. However, the role was recast, with Mika Amonsen taking over.

Coshowrunner Brandon Margolis explained that the recasting was a creative choice, saying the new story needed “a different energy” and allowed the show to explore Danny as the father of a cop for the first time. The writers felt it opened new storytelling opportunities while keeping the same character and father-son relationship.

Amonsen acknowledged fan backlash but said many viewers have been supportive. He shared that he felt pressure to honor Terraciano’s version of Sean and made deliberate choices to stay true to the character, including studying later seasons of Blue Bloods.

Terraciano later addressed the change publicly, expressing gratitude for his time on the show and support for Amonsen. He revealed that Wahlberg personally called him after the news broke, which he described as a meaningful and emotional moment.

Ultimately, Boston Blue focuses on Sean’s growth as a young officer and his evolving relationship with Danny, while introducing a new era for the Reagan family.