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

Blue Bloods' viewers are finally getting an explanation for why Donnie Wahlberg’s character, Danny, moved in the 'Boston Blue' spinoff

CBS’s upcoming “Blue Bloods” spinoff has recast Danny Reagan’s son after the same actor played the recurring role throughout the original 14 seasons. Andrew Terraciano will not return as Sean Reagan in “Boston Blue” after appearing in nearly every episode across 14 seasons as the son of Donnie Wahlberg’s character,