Only Son Meaning

Example: Used other than as an idiom: see only,‎ son.
  He was the only son to go to college.
A sole male child among multiple siblings.
1991 November 18, Alessandra Stanley, “The Symbols Spawned by a Killing”, New York Times:
  Mr. Doyle, an only son, grew up with the undivided attention of affectionate parents and two doting sisters.