Frank's detail/bodyguard
Anyone know who Frank's shadow is? He's a guy with white/silver/grey hair. Often seen in the background, but never (or almost never?) heard. I don't know the character's name, and I don't know the actor's name. I don't see him under 'full cast' either.
(I do see a person listed as Detective Nuciforo, with no picture on imdb. Apparently he's a real detective and also serves as the show's police technical advisor. So all those complainers who think this show does a sloppy job on police procedures now know who they can complain to. )
Also, I know this isn't gospel (or canon, as the purists would say), but the Blue BLoods wikia (which is NOT the same as Wikipedia) lists Frank's age as 58. And yes, when I read that I practically fell over laughing.