Boston Blue made a shocking cast change for the role of Danny Reagan’s son, Sean.

was added to the cast of the Blue Bloods spinoff, according to a Wednesday, July 9, report from The Hollywood Reporter. Amonsen, 35, will play Sean, the youngest son of ’s beloved character.

On Blue Bloods, the role was originally played by for the entirety of the show’s 14 seasons. A reason for the abrupt recasting was not immediately given.

Blue Bloods, which premiered in 2010, followed the Reagan family as they worked for the NYPD. The procedural came to an end in December 2024. Following its series finale, CBS announced that Blue Bloods was getting the spinoff treatment with Boston Blue.

“So excited to carry on the tradition, to share so many surprises, to answer some unanswered questions and to welcome all of you — to #BostonBlue!” Wahlberg wrote via Instagram in March 2025. “The next chapter in the #BlueBloods legacy begins. I can’t wait. See you CBS fall! 💙❤️🫡🙏🏼.”

While Boston Blue was in the early stages, Wahlberg teased that there would be potential for some Blue Bloods cameos.

“The viewers are saying, ‘How do we keep going with a Blue Bloods spinoff without the whole family?’ And I share that. How do we do that, right?” he said in a June interview with Fox News Digital.

Wahlberg added that Boston Blue would continue to build upon Blue Bloods‘ legacy.

“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,” he told the outlet. “There’ll always be a Reagan a phone call away And the traditions that the Reagans have, Danny wouldn’t abandon those traditions.”

In addition to Wahlberg and Amonsen, Boston Blue will also star , , , Gloria Reuben and Ernie Hudson.

Boston Blue is set to follow Danny as he moves to Boston to join their police force. He is partnered up with Detective Lena Silver (Martin-Green), the eldest daughter of a prominent law enforcement family.

Sean also relocated to Beantown to become a patrolman for the Boston PD as he had a desire to serve outside of his hometown.

Wahlberg gave fans a sneak peek of the Boston Blue table read earlier this month.

“A new chapter 💙,” the actor captioned the post and tagged Martin-Green in the post.