You know your children are growing up when they stop asking you where they came from and refuse to tell you where they’re going.

The joke hinges on a reversal of parental expectations. Small children ask literal questions—about birth, bodies, and origins—because parents are their primary source of knowledge. As children mature, the questions stop not because curiosity ends, but because independence and embarrassment grow; they seek answers elsewhere. The second half sharpens the point: adolescence is marked by secrecy and self-determination, so the parent who once explained everything now receives less information. Beneath the humor is a concise portrait of parental loss of control: growing up means moving from innocence and openness to autonomy and guardedness, leaving parents nostalgic and uneasy.