Mika Amonsen will replace Andrew Terraciano, who played Sean Reagan throughout the 14-season run of "Blue Bloods."Though Donnie Wahlberg is the only member of the core Blue Bloods cast set to return for the long-running series' first spinoff,

Danny Reagan’s youngest son Sean will look a little different when he appears alongside his dad on CBS’ upcoming drama series Boston Blue. Mika Amonsen has been cast as a series regular opposite Donnie Wahlberg on the Blue Bloods offshoot,

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,