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

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,

Mika Amonsen ( Thanksgiving) has joined the show’s cast as Sean Reagan, the youngest son of series lead Donnie Wahlberg’s character, Danny Reagan. Amonsen will take over the role played by Andrew Terraciano throughout Blue Bloods’ 14-season run on CBS.