“Blue Bloods,” a show centered around family and crime, distinguishes itself through the Reagan family. In its 13 seasons, the family dynamic is central. Jamie is the youngest sibling at around 36 years old. Erin is the second youngest, officially aged 48.
The debate over the eldest sibling continues, with Danny thought to be in his early 50s. Joe was originally the eldest. So, to sum it up, Jamie, Erin, Danny, and Joe are the Reagan siblings in order of age. It’s unclear if the show will change these ages, but this is the best estimate based on available information.