Moynahan will make a special guest appearance as Erin Reagan in the premiere and will also direct an upcoming episode of the spinoff

"More fun (and surprises) to come," Wahlberg teased. "Let’s go!" Donnie Wahlberg is reuniting with a key member of the Blue Bloods family. The New Kids on the Block star celebrated the announcement of his on-screen sister,

Bridget Moynahan is joining her brother in blue. The actress, 54, is officially set to return as Erin Reagan in the “Blue Bloods” spinoff, “Boston Blue.” The new show will follow Danny Reagan (Donnie Wahlberg) as he leaves the Big Apple to take a position with the Boston Police Department.