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,

CBS later announced that a spinoff titled Boston Blue was ordered straight to series and would expand the universe with Wahlberg’s character. The actor hasn’t ruled out appearances from his former onscreen family members — with Moynahan the first to be confirmed.

Sean Reagan will be accompanying his father, Danny, to Boston in "Boston Blue," but the series has recast the "Blue Bloods" spin-off's role - here's why.