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

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.

Donnie Wahlberg Celebrates ‘New Chapter’ at First 'Boston Blue’ Table Read originally appeared on Parade. Donnie Wahlberg celebrated the official start of the Blue Bloods spinoff, Boston Blue, by sharing a photo from the first table read.