M. Romero was a Human male who served as a Military Assault Command Operations soldier during the 22nd century. In the year 2153, Romero was assigned to the NX-class starship, Enterprise for it's Delphic Expanse mission.
Romero ate lunch with fellow MACOs Major Hayes, Corporal Chang, and Sergeant Kemper in the mess hall in 2153, upon their first meeting Ensign Hoshi Sato, Enterprise's communications officer. Shortly thereafter, he participated in the rescue mission to retrieve Captain Archer, Commander Tucker, and the Xindi Kessick from a trellium-mining facility. (ENT: "The Xindi")