Mika Amonsen will replace Andrew Terraciano, who played Sean Reagan throughout the 14-season run of "Blue Bloods."

Blue Bloods' viewers are finally getting an explanation for why Donnie Wahlberg’s character, Danny, moved in the 'Boston Blue' spinoff

Although “Boston Blue” is a direct offshoot of “Blue Bloods,” the Reagan family will look a bit different this time around. Mika Amonsen has joined the CBS drama in a series regular role playing the youngest son of Donnie Wahlberg's character,