Rob The Cradle Meaning

(idiomatic, disapproving) To use a young person for a purpose inappropriate to his or her age.

Example: 2004, Karen Thomas, "Cameron won't pull a Britney," USA Today, 8 Jan.,
  The actress, 31, also pooh-poohs the notion that she's robbing the cradle with Timberlake, 22.
1879, John McElroy, Andersonville: A Story of Rebel Military Prisons, ch. 29,
  They were ordered to the field, and their places filled by the Georgia "Reserves," an organization of boys under, and men over the military age. As General Grant aptly-phrased it, "They had robbed the cradle and the grave," in forming these regiments.