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,

Donnie Wahlberg is the new kid on the block in the new Blue Bloods spinoff series, which sees Danny Reagan go to Boston, and they have officially had their first table read. Wahlberg shared a photo of the very first script from his new show,

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.