rob the cradle

rob the cradle  {v. phr.},  {informal}

To have dates with or marry a person much younger than yourself.

When the old woman married a young man, everyone said she was robbing the cradle.

- cradle-robber  {n.}

The judge died when he was seventy. He was a real cradle-robber because he left a thirty-year-old widow.

- cradle-robbing  {adj.} or  {n.}