Mika Amonsen will play Sean Reagan in the 'Blue Bloods' spinoff, 'Boston Blue,' a role previously played by Andrew Terraciano.

Andrew Terraciano will not return as Sean Reagan in the spinoff, and Mika Amonsen will now take his place in 'Boston Blue'

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,