The patriarch is Francis ‘Frank’ Reagan who is the Police Commissioner. He served as a US Marine Corps officer in Vietnam before he joined the NYPD. He is also a 9/11 First Responder and also a widower. His son Joe was murdered in the line of duty and has three other children – Danny, Erin and Police Officer Jamie Reagan, played by Will Estes.
Danny is a top NYPD detective and holds the rank of Detective First Grade. He is a hard-nosed officer who does not always go by the book. Like his father, he is also a US Marine Corps veteran, having served in the Iraq War in Fallujah.
Erin is an Assistant District Attorney in Manhattan who prosecutes many of the criminals that Danny arrests. She was promoted to Deputy Trial Bureau Chief in Season 3 of “Blue Bloods.” While his brother Danny has unorthodox ways in carrying out departmental policy and tactics in making arrests, Erin is the opposite because she likes to go by the book. She is very legalistic and is always careful in making sure that prosecutions of criminals will stick.
Erin’s and Danny’s disagreements on matters of law, moral, and practical considerations are where much of the dialog of “Blue Bloods” take place.
Then there is Jamison ‘Jamie’ Reagan, the youngest Reagan who has a law degree in Harvard. After working for a law firm for some time, he decided to leave the practice and join the NYPD.